Fluorescent curable dental composition and cured product thereof

ABSTRACT

The present invention provides a dental curable composition that shows fluorescence sufficient to enable highly aesthetic harmonious restoration almost indistinguishable from surrounding natural teeth, and that, while having sufficient mechanical strength and radiopacity and good ease of polishing as a restorative material, desirably resists discoloration not only in the intraoral environment but under accelerated heating conditions and under xenon light, without losing fluorescence even under these conditions. The present invention also provides a cured product of such a dental curable composition. The present invention relates to a dental curable composition comprising a polymerizable monomer (A), an inorganic filler (B), a polymerization initiator (C), and a fluorescent agent (D), wherein the fluorescent agent (D) comprises a 9- to 11-membered benzo-fused heterocyclic compound containing two or more heteroatoms (excluding benzoimidazole compounds).

TECHNICAL FIELD

The present invention relates to a dental material that can be used forpartial or whole replacement of natural tooth in the field of dentistry,particularly a dental curable composition that can be suitably used inapplications such as dental composite resins and dental mill blanks.

BACKGROUND ART

Natural teeth show fluorescence. The fluorescence of natural teeth makesthe teeth luminous under natural light, whereas it presents abluish-white color under blacklight. This poses an issue in arestorative dental treatment when the restoration uses a non-fluorescentdental material made of a curable composition containing components suchas a polymerizable monomer and a polymerization initiator because,depending on the surrounding environment, the dental material appearsdifferent in shade and becomes distinguishable from natural teeth inareas of teeth restored with the dental material. Today's dentalmaterials are required to have high levels of aesthetic quality thatmake the restored portions almost indistinguishable from natural teeth,regardless of the environment. With the objective of improving aestheticquality, attempts have been made to provide a dental material withfluorescence, comparable to that of natural teeth, by adding an organicfluorescent dye to a dental material.

For example, Patent Literatures 1 and 2 disclose dental materialscontaining a fluorescent agent of phthalic acid esters, such as2,5-dihydroxydiethylterephthalate, in order to impart the same level offluorescence exhibited by natural teeth.

However, the fluorescent agent of phthalic acid esters described inPatent Literatures 1 and 2, when present in a dental curable compositioncontaining certain components (specifically, a dental curablecomposition containing a filler containing, for example, zirconia oralumina), is known to produce a thick shade of yellow in a cured productafter polymerization and cure. That is, there is difficulty inreproducing the shade of natural teeth.

In response to this issue, Patent Literature 3 proposes a curablecomposition that specifies the contents of an amine compound, a phthalicacid ester fluorescent agent, and a radiopaque acidic filler. However,investigations by the present inventors revealed that the compositiondescribed in Patent Literature 3 cannot provide satisfactoryfluorescence under simulated clinical conditions, and needs furtherimprovements.

Patent Literature 4 proposes an inorganic fluorescent agent that doesnot involve discoloration even in the presence of zirconia. However,common knowledge is that the fluorescence intensity of an inorganicfluorescent agent decreases with decreasing particle diameter, and, inorder to ensure sufficient fluorescence, an inorganic fluorescent agentneeds to be present in a dental curable composition in the form ofcoarse particles of several micrometers. The presence of such coarseinorganic fluorescence particles can cause various problems in dentalcomposite resins and dental resin blocks for CAD/CAM, such as a decreaseof polishability, a decrease of mechanical strength, and inconsistentfluorescence.

CITATION LIST Patent Literature

-   Patent Literature 1: JP 2(1990)-233605 A-   Patent Literature 2: JP 2009-280673 A-   Patent Literature 3: JP 2017-141188 A-   Patent Literature 4: JP 2010-222466 A

SUMMARY OF INVENTION Technical Problem

As discussed above, no dental curable composition or cured product isavailable that shows sufficient fluorescence, and that excels inaesthetics and durability while having sufficient mechanical strengthand radiopacity and retaining ease of polishing.

The present invention was made to provide a solution to the foregoingissues of related art, and an object of the present invention is toprovide a dental curable composition that shows fluorescence sufficientto enable highly aesthetic harmonious restoration almostindistinguishable from surrounding natural teeth, and that, while havingsufficient mechanical strength and radiopacity and good ease ofpolishing as a restorative material, desirably resists discoloration notonly in the intraoral environment but under accelerated heatingconditions and under xenon light, without losing fluorescence even underthese conditions. Another object of the present invention is to providea cured product of such a dental curable composition.

Solution to Problem

The present inventors conducted intensive studies to achieve theforegoing objects, and found that a dental curable composition and acured product thereof containing a compound having a specific structureshow sufficient fluorescence, and excel in aesthetics and durabilitywhile having sufficient mechanical strength and radiopacity andretaining ease of polishing.

Specifically, the present invention includes the following.

[1] A dental curable composition comprising a polymerizable monomer (A),an inorganic filler (B), a polymerization initiator (C), and afluorescent agent (D), wherein the fluorescent agent (D) comprises a 9-to 11-membered benzo-fused heterocyclic compound containing two or moreheteroatoms (excluding benzoimidazole compounds).[2] The dental curable composition according to [1], wherein the 9- to11-membered benzo-fused heterocyclic compound containing two or moreheteroatoms comprises a fluorescent agent (D-1) representing abenzo-fused 6-membered heterocyclic compound having two heteroatoms.[3] The dental curable composition according to [2], wherein thefluorescent agent (D-1) comprises a compound having a benzodiazinoneskeleton, and/or a compound having a benzoxazinone skeleton.[4] The dental curable composition according to [3], wherein thecompound having a benzodiazinone skeleton is a compound having askeleton represented by the following general formula (5),

wherein X represents a 6-membered heterocyclic ring having two nitrogenatoms, and the 6-membered heterocyclic ring has at least one oxo group,and may be optionally substituted.[5] The dental curable composition according to [3] or [4], wherein thecompound having a benzodiazinone skeleton is a compound (D-1a) having aquinazolinone skeleton.[6] The dental curable composition according to [3], wherein thefluorescent agent (D-1) comprises a compound having a benzoxazinoneskeleton.[7] The dental curable composition according to [6], wherein thecompound having a benzoxazinone skeleton is a compound having a skeletonrepresented by the following general formula (6),

wherein Y represents a 6-membered heterocyclic ring having one nitrogenatom and one oxygen atom, and the 6-membered heterocyclic ring has atleast one oxo group, and may be optionally substituted.[8] The dental curable composition according to any one of [2] to [7],wherein the fluorescent agent (D-1) is a compound having a moietyrepresented by the following general formula (1) or (2),

wherein R¹ in general formulae (1) and (2) is an oxygen atom or —NH—,and R² in general formulae (1) and (2) represents an optionallysubstituted aromatic group.[9] The dental curable composition according to any one of [2] to [7],wherein the fluorescent agent (D-1) comprises at least one compoundselected from the group consisting of2-(2-hydroxyphenyl)-4(1H)-quinazolinone,2-(2-hydroxyphenyl)-4H-3,1-benzoxazin-4-one,N-[2-(4(1H)-quinazolinon-2-yl)phenyl]benzenesulfoneamide,N-[2-(4-oxo-1,3-benzoxazin-2-yl)phenyl]benzenesulfoneamide,7-dimethylamino-3-[2-[4-(trifluoromethyl)phenyl]ethenyl]-2H-1,4-benzoxazin-2-one,7-dimethylamino-3-[2-[2,3,4,5,6-pentafluorophenyl]ethenyl]-2H-1,4-benzoxazin-2-one,and7-dimethylamino-3-[2-[2,4-bis(trifluoromethyl)phenyl]ethenyl]-2H-1,4-benzoxazin-2-one.[10] The dental curable composition according to any one of [2] to [9],wherein the fluorescent agent (D) further comprises a fluorescent agent(D-2) representing a benzo-fused 5-membered heterocyclic compound havingone nitrogen atom and one oxygen atom.[11] The dental curable composition according to [10], wherein thefluorescent agent (D-2) is a fluorescent agent (D-2a) representing acompound having a benzoxazole skeleton.[12] The dental curable composition according to [11], wherein thefluorescent agent (D-2a) is a compound having a moiety represented bythe following general formula (3),

wherein R³ represents an optionally substituted aromatic group, or anoptionally substituted vinylene group.[13] The dental curable composition according to [11] or [12], whereinthe fluorescent agent (D-2a) is a compound represented by the followingformula (12).

[14] The dental curable composition according to any one of [1] to [13],wherein the inorganic filler (B) is an inorganic filler containing atleast one metal compound selected from the group consisting of zirconiumoxide, aluminum oxide, ytterbium oxide, and ytterbium fluoride.[15] The dental curable composition according to any one of [1] to [14],wherein the inorganic filler (B) has a specific surface area of 10 to300 m²/g.[16] A dental composite resin comprising a dental curable composition ofany one of [1] to [15].[17] A dental mill blank comprising a cured product of a dental curablecomposition of any one of [1] to [15].

Advantageous Effects of Invention

According to the present invention, a dental curable composition can beprovided that shows fluorescence sufficient to enable highly aestheticharmonious restoration almost indistinguishable from surrounding naturalteeth, and that, while having sufficient mechanical strength andradiopacity and good ease of polishing as a restorative material,desirably resists discoloration not only in the intraoral environmentbut under accelerated heating conditions and under xenon light, withoutlosing fluorescence even under these conditions. The present inventioncan also provide a cured product of such a dental curable composition. Adental curable composition and a cured product thereof according to thepresent invention can be suitably used in applications such as dentalcomposite resins and dental mill blanks.

DESCRIPTION OF EMBODIMENTS

The present invention is described below in detail. A dental curablecomposition of the present invention comprises a polymerizable monomer(A), an inorganic filler (B), a polymerization initiator (C), and afluorescent agent (D), wherein the fluorescent agent (D) comprises a 9-to 11-membered benzo-fused heterocyclic compound containing two or moreheteroatoms (excluding benzoimidazole compounds). A dental curablecomposition and a cured product thereof having this configuration showsufficient fluorescence, and excel in aesthetics and durability whilehaving sufficient mechanical strength, radiopacity, and ease ofpolishing, making it suitable for use in applications such as dentalcomposite resins and dental mill blanks.

Polymerizable Monomer (A)

The polymerizable monomer (A) in a dental curable composition of thepresent invention may be a known polymerizable monomer used for dentalcurable compositions, particularly preferably a radical polymerizablemonomer. Examples of the radical polymerizable monomer include esters ofunsaturated carboxylic acids such as α-cyanoacrylic acid, (meth)acrylicacid, α-halogenated acrylic acid, crotonic acid, cinnamic acid, sorbicacid, maleic acid, and itaconic acid; (meth)acrylamide; derivatives of(meth)acrylamide; vinyl esters; vinyl ethers; mono-N-vinyl derivatives;and styrene derivatives. The polymerizable monomer (A) may be usedalone, or two or more thereof may be used in combination. Preferred areesters of unsaturated carboxylic acids, and derivatives of(meth)acrylamide. Esters of (meth)acrylic acid, and derivatives of(meth)acrylamide are more preferred, and esters of (meth)acrylic acidare even more preferred. As used herein, the term “(meth)acryl” isintended to be inclusive of both methacryl and acryl. The term“(meth)acrylic monomer” is intended to be inclusive of both(meth)acrylic acid esters and derivatives of (meth)acrylamide. Examplesof (meth)acrylic acid esters and derivatives of (meth)acrylamide are asfollows.

(i) Monofunctional (Meth)Acrylic Acid Esters and Derivatives of(Meth)Acrylamide

Examples include methyl (meth)acrylate, isobutyl (meth)acrylate, benzyl(meth)acrylate, dodecyl (meth)acrylate, 2-(N,N-dimethylamino)ethyl(meth)acrylate, 2,3-dibromopropyl (meth)acrylate,3-(meth)acryloyloxypropyltrimethoxysilane,11-(meth)acryloyloxyundecyltrimethoxysilane, 2-hydroxyethyl(meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl(meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl(meth)acrylate, propylene glycol mono(meth)acrylate, glycerinmono(meth)acrylate, erythritol mono(meth)acrylate, phenoxyethyleneglycol (meth)acrylate, isobornyl (meth)acrylate, 3-phenoxybenzyl(meth)acrylate, N-methylol (meth)acrylamide, N-hydroxyethyl(meth)acrylamide, N,N-bis(hydroxyethyl)(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-di-n-propyl(meth)acrylamide, N-ethyl-N-methyl (meth)acrylamide,(meth)acryloylmorpholine, (meth)acryloyloxydodecylpyridinium bromide,(meth)acryloyloxydodecylpyridinium chloride,(meth)acryloyloxyhexadecylpyridinium bromide,(meth)acryloyloxyhexadecylpyridinium chloride,ethoxylated-o-phenylphenol (meth)acrylate, ethoxylated-m-phenylphenol(meth)acrylate, ethoxylated-p-phenylphenol (meth)acrylate,propoxylated-o-phenylphenol (meth)acrylate, propoxylated-m-phenylphenol(meth)acrylate, propoxylated-p-phenylphenol (meth)acrylate,o-phenoxybenzyl (meth)acrylate, m-phenoxybenzyl (meth)acrylate,p-phenoxybenzyl (meth)acrylate, 2-(o-phenoxyphenyl)ethyl (meth)acrylate,2-(m-phenoxyphenyl)ethyl (meth)acrylate, and 2-(p-phenoxyphenyl)ethyl(meth)acrylate. In view of improving ease of handling of a paste of thedental curable composition obtained and providing desirable mechanicalstrength after cure, ethoxylated-o-phenylphenol (meth)acrylate andm-phenoxybenzyl (meth)acrylate are most preferred.

(ii) Bifunctional (Meth)Acrylic Acid Esters

Examples include aromatic bifunctional (meth)acrylic acid esters, andaliphatic bifunctional (meth)acrylic acid esters.

Examples of aromatic bifunctional (meth)acrylic acid esters include2,2-bis((meth)acryloyloxyphenyl)propane,2,2-bis[4-(3-acryloyloxy-2-hydroxypropoxy)phenyl]propane,2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane (commonlyknown as Bis-GMA), 2,2-bis(4-(meth)acryloyloxypolyethoxyphenyl)propane,2-(4-(meth)acryloyloxydiethoxyphenyl)-2-(4-(meth)acryloyloxyethoxyphenyl)propane,2-(4-(meth)acryloyloxydiethoxyphenyl)-2-(4-(meth)acryloyloxytriethoxyphenyl)propane,2,2-bis(4-(meth)acryloyloxypropoxyphenyl)propane,2,2-bis(4-(meth)acryloyloxyisopropoxyphenyl)propane,2,2-bis(4-(meth)acryloyloxydipropoxyphenyl)propane,2-(4-(meth)acryloyloxydipropoxyphenyl)-2-(4-(meth)acryloyloxytriethoxyphenyl)propane,9,9-bis[4-(2-(meth)acryloyloxyethoxy)phenyl]fluorene,9,9-bis[4-(2-(meth)acryloyloxypolyethoxy)phenyl]fluorene, diphenylbis[3-(meth)acryloyloxypropyl]silane, and methylphenylbis[3-(meth)acryloyloxypropyl]silane.

Examples of aliphatic bifunctional (meth)acrylic acid esters includeglycerol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethyleneglycol di(meth)acrylate, triethylene glycol diacrylate, triethyleneglycol dimethacrylate (commonly known as 3G), propylene glycoldi(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycoldi(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,5-pentanedioldi(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,10-decanedioldi(meth)acrylate, 1,12-dodecanediol di(meth)acrylate,1,2-bis(3-(meth)acryloyloxy-2-hydroxypropyloxy)ethane,tricyclodecanedimethanol di(meth)acrylate,2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl)diacrylate,2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl)dimethacrylate(commonly known as UDMA), and dicyclohexylbis[3-(meth)acryloyloxypropyl]silane.

In view of advantages such as improved ease of handling of the dentalcurable composition and improved mechanical strength of the curedproduct produced, the bifunctional (meth)acrylic acid esters arepreferably 2,2-bis[4-(3-acryloyloxy-2-hydroxypropoxy)phenyl]propane,2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane (Bis-GMA),2,2-bis(4-(meth)acryloyloxypolyethoxyphenyl)propane (average number ofmoles of ethyleneoxy group added: 1 to 30), triethylene glycoldiacrylate, triethylene glycol dimethacrylate (3G), 1,10-decanedioldi(meth)acrylate, 1,12-dodecanediol di(meth)acrylate,1,2-bis(3-(meth)acryloyloxy-2-hydroxypropyloxy)ethane, tricyclodecanedimethanol di(meth)acrylate,2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl)diacrylate, and2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl)dimethacrylate(UDMA), more preferably2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane (Bis-GMA),2,2-bis(4-methacryloyloxypolyethoxyphenyl)propane (average number ofmoles of ethyleneoxy group added: 1 to 30), triethylene glycoldimethacrylate (3G), 1,10-decanediol dimethacrylate, 1,12-dodecanedioldimethacrylate, 1,2-bis(3-methacryloyloxy-2-hydroxypropyloxy)ethane,tricyclodecanedimethanol dimethacrylate, and2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl)dimethacrylate(UDMA), even more preferably2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane (Bis-GMA),2,2-bis(4-methacryloyloxypolyethoxyphenyl)propane (average number ofmoles of ethyleneoxy group added is about 2.6), and triethylene glycoldimethacrylate (3G).

(iii) Tri- and Higher-Functional (Meth)Acrylic Acid Esters

Examples include trimethylolpropane tri(meth)acrylate, trimethylolethanetri(meth)acrylate, trimethylolmethane tri(meth)acrylate, pentaerythritoltri(meth)acrylate, pentaerythritol tetra(meth)acrylate,dipentaerythritol tri(meth)acrylate, dipentaerythritoltetra(meth)acrylate, dipentaerythritol penta(meth)acrylate,N,N′-(2,2,4-trimethylhexamethylene)bis[2-(aminocarboxy)propane-1,3-diol]tetra(meth)acrylate,and1,7-di(meth)acryloyloxy-2,2,6,6-tetra(meth)acryloyloxymethyl-4-oxaheptane.

In view of advantages such as improved adhesive properties of the dentalcurable composition to materials such as tooth structure, metal, andceramic, the polymerizable monomer (A) may in some cases preferablyinclude a functional monomer with which the dental curable compositioncan have adhesive properties to such adherends.

In view of having desirable adhesive properties to tooth structure andbase metal, the functional monomer may be, for example, a polymerizablemonomer having a phosphoric acid group, such as 2-(meth)acryloyloxyethyldihydrogen phosphate, 10-(meth)acryloyloxydecyl dihydrogen phosphate, or2-(meth)acryloyloxyethylphenyl hydrogen phosphate; or a polymerizablemonomer having a carboxylic acid group, such as11-(meth)acryloyloxyundecane-1,1-dicarboxylic acid, or4-(meth)acryloyloxyethoxycarbonylphthalic acid. In view of havingdesirable adhesive properties to noble metals, the functional monomermay be, for example, 10-mercaptodecyl (meth)acrylate,6-(4-vinylbenzyl-n-propyl)amino-1,3,5-triazine-2,4-dithione, any of thethiouracil derivatives mentioned in JP-A-10(1998)-1473, or any of thecompounds having a sulfur element mentioned in JP-A-11(1999)-92461. Inview of effectiveness of bonding to ceramics, porcelains, and otherdental curable compositions, the functional monomer may be, for example,a silane coupling agent such asγ-(meth)acryloyloxypropyltrimethoxysilane.

The content of the polymerizable monomer (A) in a dental curablecomposition of the present invention is not particularly limited.However, in view of considerations such as ease of handling of thedental curable composition obtained or mechanical strength of the curedproduct, the content of polymerizable monomer (A) is preferably 1 mass %or more, more preferably 2 mass % or more, even more preferably 5 mass %or more, or may be 8 mass % or more, or 15 mass % or more, and ispreferably 70 mass % or less, more preferably 50 mass % or less, evenmore preferably 40 mass % or less, particularly preferably 30 mass % orless, based on the total mass of the dental curable composition. Thecontent of the polymerizable monomer (A) in a dental curable compositionof the present invention is preferably at least 3 parts by mass, morepreferably at least 4 parts by mass, even more preferably at least 5parts by mass, particularly preferably at least 10 parts by mass, and ispreferably at most 90 parts by mass, more preferably at most 70 parts bymass, even more preferably at most 60 parts by mass, particularlypreferably at most 35 parts by mass based on total 100 parts by mass ofpolymerizable monomer (A) and inorganic filler (B).

Inorganic Filler (B)

A dental curable composition of the present invention comprises aninorganic filler (B).

The inorganic filler (B) has an average particle diameter of preferably0.01 μm or more, more preferably 0.05 μm or more, even more preferably0.1 μm or more. The average particle diameter of inorganic filler (B)may be 0.2 μm or more. The inorganic filler (B) has an average particlediameter of preferably 50 μm or less, more preferably 20 μm or less,even more preferably 10 μm or less, particularly preferably 7 μm orless. With the average particle diameter of inorganic filler (B) havingthese lower limits, the dental curable composition obtained can moreeffectively reduce stickiness, and ease of handling improves. With theaverage particle diameter of inorganic filler (B) having the foregoingupper limits, the dental curable composition obtained can moreeffectively reduce runniness or roughness, and ease of handlingimproves. When the inorganic filler (B) is an agglomerated particle(secondary particle), the average particle diameter of inorganic filler(B) means an average particle diameter of the agglomerated particle(secondary particle).

The average particle diameter of inorganic filler (B) can be determinedby using a laser diffraction scattering method, or by observingparticles with an electron microscope. Specifically, a laser diffractionscattering method is more convenient for particles of 0.1 μm or greater,whereas electron microscopy is a more convenient method of particlediameter measurement for ultrafine particles of less than 0.1 μm. Here,0.1 μm is a measured value by a laser diffraction scattering method. Forexample, in the case of a laser diffraction scattering method, theaverage particle diameter can be measured by volume with a laserdiffraction particle size distribution analyzer (e.g., SALD-2300manufactured by Shimadzu Corporation), using ethanol or a 0.2% sodiumhexametaphosphate aqueous solution as dispersion medium. For electronmicroscopy, a scanning electron microscope (e.g., SU3800 or S-4000manufactured by Hitachi High-Technologies Corporation) may be used. Inelectron microscopy, for example, particles may be photographed with anelectron microscope, and the size of particles (at least 200 particles)observed in a unit field of the captured image may be measured usingimage-analyzing particle-size-distribution measurement software(Macview, manufactured by Mountech Co., Ltd.). Here, the particlediameter is determined as an arithmetic mean value of the maximum andminimum lengths of particles, and the average primary particle diameteris calculated from the number of particles and the particle diameter.More specifically, the average particle diameter of inorganic filler (B)can be measured using the method described in the EXAMPLES section.

The overall shape of particles of inorganic filler (B) is notparticularly limited, and the inorganic filler (B) may be used in theform of an irregularly shaped powder or a spherical powder. A dentalcurable composition produced with an irregularly shaped inorganic filler(B) can provide a cured product that particularly excels in mechanicalstrength and wear resistance. A dental curable composition produced witha spherical inorganic filler (B) can have smoother and more flowablepaste properties, and improved ease of handling. The overall shape ofinorganic filler (B) can be appropriately selected according to intendeduse of the dental curable composition.

Examples of the inorganic filler (B) include various types of glasses.(For example, glasses containing silica as a main component, and,optionally, oxides of elements such as heavy metals, boron, andaluminum. Examples include glass powders of common compositions, forexample, such as fused silica, quartz, soda-lime-silica glass, E glass,C glass, and borosilicate glass (PYREX® glass); and dental glasspowders, such as barium glass (for example, GM27884 and 8235manufactured by Schott, and E-2000 and E-3000 manufactured by Esstech),strontium-borosilicate glass (for example, E-4000 manufactured byEsstech), lanthanum glass-ceramics (for example, GM31684 manufactured bySchott), and fluoroaluminosilicate glass (for example, GM35429,G018-091, and G018-117 manufactured by Schott)). Other examples ofinorganic filler (B) include ceramics, alumina, composite oxides (e.g.,silica-titania, silica-zirconia, silica-ytterbia), diatomaceous earth,kaolin, clay minerals (e.g., montmorillonite), activated earth,synthetic zeolite, mica, calcium fluoride, ytterbium fluoride, yttriumfluoride, calcium phosphate, barium sulfate, zirconium oxide, titaniumoxide, and hydroxyapatite. These may be used alone, or two or morethereof may be used in combination. The inorganic filler (B) ispreferably one containing silica as a main component (containing atleast 5 mass %, preferably at least 10 mass % silica). Preferably, adental curable composition of the present invention comprises aninorganic filler containing a high-radiopacity metal compound such aszirconium oxide, aluminum oxide, or ytterbium oxide (for example, bariumglass, alumina, silica-titania, silica-zirconia, silica-ytterbia), orytterbium fluoride.

In the present invention, because of the tendency to improve ease ofpolishing, the inorganic filler (B) has a specific surface area ofpreferably 10 m²/g or more, more preferably 15 m²/g or more, even morepreferably 18 m²/g or more, particularly preferably 20 m²/g or more, andis 300 m²/g or less, preferably 250 m²/g or less, more preferably 200m²/g or less, or may be 190 m²/g or less, 170 m²/g or less, or 150 m²/gor less. Ease of polishing improves even more greatly with the specificsurface area of inorganic filler (B) having these lower limits. Bysetting the foregoing upper limits for the specific surface area ofinorganic filler (B), the inorganic filler (B) can be added in increasedamounts, and the mechanical strength of the cured product improves. Whenthe inorganic filler (B) is an agglomerated particle (secondaryparticle), the specific surface area of inorganic filler (B) means aspecific surface area of the agglomerated particle (secondary particle).

The specific surface area of inorganic filler (B) can be measured byusing the BET method. Specifically, for example, a specific surface areameasurement device (e.g., the BELSORP-mini series manufactured byMicrotracBEL Corp.) can be used for the measurement of specific surfacearea. When finding the specific surface area of inorganic filler (B)using this method for example, it is preferable to measure the specificsurface area after ashing the inorganic filler (B) in advance, forexample, by processing the inorganic filler (B) at 450° C. for 4 hours,in order to eliminate the influence of organic materials when theinorganic filler (B) is surface treated (described later) or when theinorganic filler (B) is an organic-inorganic composite filler.Preferably, such ashing is also performed when determining the specificsurface area of the inorganic filler (B) contained in the dental curablecomposition. More specifically, the specific surface area of inorganicfiller (B) can be measured using the method described in the EXAMPLESsection.

In the present invention, the inorganic filler (B) may have a form of anagglomerated particle formed by agglomeration of the inorganic filler.Commercially available inorganic fillers typically exist in the form ofaggregates. The cohesion of commercially available inorganic fillers isso weak that these fillers break into particle sizes indicated by themanufacturer when 10 mg of its powder is added and ultrasonicallydispersed at 40 W and 39 KHz for 30 minutes in 300 mL of water or in thesame amount of a dispersion medium prepared by adding a surfactant(e.g., at most 5 mass % of sodium hexametaphosphate) to water. Incontrast, the agglomerated particles in the present invention arestrongly held together, and become hardly dispersed even under theseconditions.

In a preferred method of preparing a strong agglomerate of particlesfrom an aggregate of commercially available inorganic fillers, theinorganic filler is heated to a temperature range just below thetemperature that melts the inorganic filler so that the adjoininginorganic filler particles under the applied heat lightly fuse togetherand increase cohesion. Here, the inorganic filler may have a form of anaggregate before heating, in order to control the shape of theagglomerated particle. An aggregate can be formed, for example, byapplying pressure to the inorganic filler placed in a suitablecontainer, or by dispersing the inorganic filler in a solvent, andremoving the solvent using a method such as spray drying.

In another preferred method of preparing an agglomerated particle formedby strong aggregation of inorganic filler particles, a sol such as asilica sol, an alumina sol, a titania sol, or a zirconia sol prepared byusing a wet method is dried using a method such as freeze drying orspray drying, and optionally subjected to a heat treatment. In this way,an agglomerated particle formed by strong aggregation of particles canbe obtained with ease. Specific examples of the sols include finespherical silica particles (Seahostar® manufactured by Nippon ShokubaiCo., Ltd. under this trade name; e.g., the KE series, a surface-treatedtype), a silica organosol (OSCAL® manufactured by JGC C & C under thistrade name), a titania sol (QUEEN TITANIC series manufactured by NissanChemical Corporation under this trade name), a silica sol (SNOWTEX®manufactured by Nissan Chemical Corporation under this trade name), analumina sol (Aluminasol-100, Aluminasol-200, Aluminasol-520 manufacturedby Nissan Chemical Corporation under these trade names), and a zirconiasol (NanoUse® ZR series manufactured by Nissan Chemical Corporationunder this trade name). The shape of the inorganic filler particle isnot particularly limited, and may be appropriately selected for use.

In the present invention, the inorganic filler (B) may be present as anorganic-inorganic composite filler in the dental curable composition.The organic-inorganic composite filler means a filler containing theinorganic filler and a polymer of a polymerizable monomer.

The organic-inorganic composite filler in the present invention ispreferably one in which an inorganic filler having an average particlediameter of 5 μm or less is dispersed in an organic matrix. The averageparticle diameter of the inorganic filler is more preferably 2 μm orless, even more preferably 1 μm or less.

The method of preparation of organic-inorganic composite filler is notparticularly limited in the present invention. For example, theorganic-inorganic composite filler can be prepared by adding a knownpolymerizable monomer and a known polymerization initiator to theinorganic filler, polymerizing the filler mixture in paste form by apolymerization method such as solution polymerization, suspensionpolymerization, emulsion polymerization, or bulk polymerization, andpulverizing the resulting polymer.

The refractive index of inorganic filler (B) is not particularlylimited. However, the transparency of the cured product can more easilyincrease when the inorganic filler (B) has a refractive index close tothe refractive indices of the components other than the inorganic filler(B) in the dental curable composition. In this respect, the refractiveindex of inorganic filler (B) is preferably 1.45 or more, morepreferably 1.50 or more, even more preferably 1.51 or more, and ispreferably 1.63 or less, more preferably 1.60 or less, even morepreferably 1.58 or less. The refractive index of inorganic filler (B)can be controlled, for example, by changing the type or proportion ofthe metallic elements contained in the inorganic filler (B).

A surface treatment of inorganic filler (B) is not necessarily required.However, a surface treatment is preferred because it provides a numberof advantages, including improved compatibility with polymerizablemonomer (A) as a result of hydrophobization of the surface of inorganicfiller (B), allowing the inorganic filler (B) to be added in increasedamounts. A surface treatment agent may be used for surface treatment.The type of surface treatment agent is not particularly limited, and aknown surface treatment agent may be used, for example, such as a silanecoupling agent, an organotitanium coupling agent, an organozirconiumcoupling agent, or an organoaluminum coupling agent. The surfacetreatment agent may be used alone, or two or more thereof may be used incombination. A silane coupling agent is preferred in view ofconsiderations such as compatibility between polymerizable monomer (A)and inorganic filler (B), and availability.

The silane coupling agent is preferably a compound represented by thefollowing general formula (4), though the type of silane coupling agentis not particularly limited.

[Chem. 7]

H₂C═CR⁴—CO—R⁶—(CH₂)_(q)—SiR⁶ _(p)R⁷ _((3-p))  (4)

wherein R⁴ is a hydrogen atom or a methyl group, R⁵ is an oxygen atom, asulfur atom, or —NR⁸— (R⁸ is a hydrogen atom, or an aliphatic grouphaving 1 to 8 carbon atoms; the aliphatic group may be linear, branched,or cyclic), R⁶ is a hydrolyzable group, R⁷ is a hydrocarbon group having1 to 6 carbon atoms, p is an integer of 1 to 3, q is an integer of 1 to13, and a plurality of R⁶ and R⁷ each may be the same or different fromeach other.

In the general formula (4), R⁴ is a hydrogen atom or a methyl group,preferably a methyl group. R⁵ is an oxygen atom, a sulfur atom, or—NR⁸—, preferably an oxygen atom. R⁸ is a hydrogen atom, or an aliphaticgroup having 1 to 8 carbon atoms (may be linear, branched, or cyclic),and the C1 to C8 aliphatic group represented by R⁸ may be a saturatedaliphatic group (for example, an alkyl group, or a cycloalkylene groupsuch as a cyclohexyl group), or an unsaturated aliphatic group (forexample, an alkenyl group or an alkynyl group). In view ofconsiderations such as availability, ease of production, and chemicalstability, R⁸ is preferably a saturated aliphatic group, more preferablyan alkyl group. Examples of the alkyl group include methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl,isopentyl, n-hexyl, n-heptyl, 2-methylhexyl, and n-octyl. R⁸ ispreferably a hydrogen atom, or an alkyl group having 1 to 4 carbonatoms, more preferably a hydrogen atom, or an alkyl group having 1 to 3carbon atoms, even more preferably a hydrogen atom.

In the general formula (4), examples of the hydrolyzable grouprepresented by R⁶ include alkoxy groups such as a methoxy group, anethoxy group, and a butoxy group; halogen atoms such as a chlorine atomand a bromine atom; and an isocyanate group. When a plurality of R⁶exists, the plurality of R⁶ may be the same or different from eachother. R⁶ is preferably an alkoxy group, more preferably a methoxy groupor an ethoxy group, even more preferably a methoxy group.

In the general formula (4), the C1 to C6 hydrocarbon group representedby R⁷ may be, for example, an alkyl group having 1 to 6 carbon atoms(may be cyclic), an alkenyl group having 2 to 6 carbon atoms (may becyclic), or an alkynyl group having 2 to 6 carbon atoms. When aplurality of R⁷ exists, the plurality of R⁷ may be the same or differentfrom each other.

Examples of the alkyl group having 1 to 6 carbon atoms include methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,n-pentyl, isopentyl, neopentyl, tert-pentyl, n-hexyl, cyclopropyl,cyclobutyl, cyclopentyl, and cyclohexyl.

Examples of the alkenyl group having 2 to 6 carbon atoms include vinyl,allyl, 1-methylvinyl, 1-propenyl, butenyl, pentenyl, hexenyl,cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl.

Examples of the alkynyl group having 2 to 6 carbon atoms includeethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 1-methyl-2-propynyl,2-butynyl, 3-butynyl, 1-pentynyl, 1-ethyl-2-propynyl, 2-pentynyl,3-pentynyl, 1-methyl-2-butynyl, 4-pentynyl, 1-methyl-3-butynyl,2-methyl-3-butynyl, 1-hexynyl, 2-hexynyl, 1-ethyl-2-butynyl, 3-hexynyl,1-methyl-2-pentynyl, 1-methyl-3-pentynyl, 4-methyl-1-pentynyl,3-methyl-1-pentynyl, 5-hexynyl, and 1-ethyl-3-butynyl.

In the general formula (4), p is an integer of 1 to 3, preferably 2 or3, more preferably 3. In the general formula (4), q is an integer of 1to 13, preferably an integer of 2 to 12, more preferably an integer of 3to 11.

Specific examples of the silane coupling agent represented by thegeneral formula (4) include methacryloyloxymethyltrimethoxysilane,2-methacryloyloxyethyltrimethoxysilane,3-methacryloyloxypropyltrimethoxysilane,4-methacryloyloxybutyltrimethoxysilane,5-methacryloyloxypentyltrimethoxysilane,6-methacryloyloxyhexyltrimethoxysilane,7-methacryloyloxyheptyltrimethoxysilane,8-methacryloyloxyoctyltrimethoxysilane,9-methacryloyloxynonyltrimethoxysilane,10-methacryloyloxydecyltrimethoxysilane,11-methacryloyloxyundecyltrimethoxysilane,12-methacryloyloxydodecyltrimethoxysilane,13-methacryloyloxytridecyltrimethoxysilane,11-methacryloyloxyundecyldichloromethylsilane,11-methacryloyloxyundecyltrichlorosilane, and12-methacryloyloxydodecyldimethoxymethylsilane. The silane couplingagent may be used alone, or two or more thereof may be used incombination. In view of availability, the silane coupling agent ispreferably 3-methacryloyloxypropyltrimethoxysilane. In view of furtherimprovement of compatibility between polymerizable monomer (A) andinorganic filler (B), the silane coupling agent is preferably8-methacryloyloxyoctyltrimethoxysilane,9-methacryloyloxynonyltrimethoxysilane,10-methacryloyloxydecyltrimethoxysilane, or11-methacryloyloxyundecyltrimethoxysilane.

The method of surface treatment is not particularly limited, and a knownmethod may be used.

The amount of surface treatment agent is not particularly limited.However, the surface treatment agent may be used in an amount of, forexample, at least 1 part by mass relative to 100 parts by mass of thefiller before surface treatment. The amount of surface treatment agentis preferably at least 5 parts by mass, more preferably at least 6 partsby mass, even more preferably at least 8 parts by mass, particularlypreferably at least 10 parts by mass, most preferably at least 20 partsby mass, and is preferably at most 50 parts by mass, more preferably atmost 45 parts by mass, even more preferably at most 40 parts by mass.With the surface treatment agent used within these lower limits, themechanical strength of the cured product produced more easily improves.With the foregoing upper limits, a decrease of mechanical strength inthe cured product due to excess amounts of surface treatment agent canbe reduced.

The content of the inorganic filler (B) in a dental curable compositionof the present invention is not particularly limited (the content ofinorganic filler (B) after surface treatment when the inorganic filler(B) is surface treated). However, in view of considerations such as easeof handling of the dental curable composition and the mechanicalstrength of the cured product produced, the content of the inorganicfiller (B) is preferably 10 mass % or more, more preferably 30 mass % ormore, even more preferably 50 mass % or more, particularly preferably 65mass % or more, and is preferably 97 mass % or less, more preferably 96mass % or less, even more preferably 95 mass % or less, particularlypreferably 90 mass % or less, based on the total mass of the dentalcurable composition. With the inorganic filler (B) being present withinthese lower limits, the dental curable composition can have improvedease of handling because of more effectively reduced stickiness, and thecured product can have improved mechanical strength. With the inorganicfiller (B) being present within the foregoing upper limits, the dentalcurable composition can be prevented from becoming excessively hard, andease of handling improves. The content of the inorganic filler (B) in adental curable composition of the present invention is preferably atleast 10 parts by mass, more preferably at least 30 parts by mass, evenmore preferably at least 50 parts by mass, particularly preferably atleast 65 parts by mass, and is preferably at most 97 parts by mass, morepreferably at most 96 parts by mass, even more preferably at most 95parts by mass, particularly preferably at most 90 parts by mass based ontotal 100 parts by mass of polymerizable monomer (A) and inorganicfiller (B).

A dental curable composition of the present invention may comprise anorganic filler. Examples of the organic filler include acrylic polymers(such as polymethyl methacrylate, polyethyl methacrylate, a methylmethacrylate-ethyl methacrylate copolymer, crosslinked polymethylmethacrylate, crosslinked polyethyl methacrylate, and polyamides),polyvinyl chloride, polystyrene, chloroprene rubber, nitrile rubber, anethylene-vinyl acetate copolymer, a styrene-butadiene copolymer, anacrylonitrile-styrene copolymer, and an acrylonitrile-styrene-butadienecopolymer. These may be used alone, or two or more thereof may be usedas a mixture. The shape of organic filler is not particularly limited,and the particle size of organic filler may be appropriately selectedfor use. In view of considerations such as ease of handling andmechanical strength of the composition obtained, the organic filler hasan average particle diameter is preferably 0.001 to 50 μm, morepreferably 0.001 to 10 μm. The average particle diameter of organicfiller can be measured using the same method used for the measurement ofaverage particle diameter of inorganic filler (B).

Polymerization Initiator (C)

A dental curable composition of the present invention comprises apolymerization initiator (C). The polymerization initiator (C) may beselected from polymerization initiators commonly used in industry,particularly those used in dentistry. Preferred for use arephotopolymerization initiators and chemical polymerization initiators.The polymerization initiator (C) may be used alone, or two or morethereof may be used in appropriate combinations.

Examples of the photopolymerization initiators include(bis)acylphosphine oxides, ketals, α-diketones, and coumarin compounds.

Examples of acylphosphine oxides in the (bis)acylphosphine oxidesinclude 2,4,6-trimethylbenzoyldiphenylphosphine oxide,2,6-dimethoxybenzoyldiphenylphosphine oxide,2,6-dichlorobenzoyldiphenylphosphine oxide,2,4,6-trimethylbenzoylmethoxyphenylphosphine oxide,2,4,6-trimethylbenzoylethoxyphenylphosphine oxide,2,3,5,6-tetramethylbenzoyldiphenylphosphine oxide, benzoyldi(2,6-dimethylphenyl)phosphonate, and salts of these (e.g., sodiumsalts, potassium salts, and ammonium salts). Examples ofbisacylphosphine oxides include bis(2,6-dichlorobenzoyl)phenylphosphineoxide, bis(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide,bis(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide,bis(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide,bis(2,6-dimethoxybenzoyl)phenylphosphine oxide,bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide,bis(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide,bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide,bis(2,5,6-trimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide, andsalts of these (e.g., sodium salts, potassium salts, and ammoniumsalts).

Particularly preferred examples of the (bis)acylphosphine oxides includesodium salts of 2,4,6-trimethylbenzoyldiphenylphosphine oxide,2,4,6-trimethylbenzoylmethoxyphenylphosphine oxide,bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and2,4,6-trimethylbenzoylphenylphosphine oxide.

Examples of the ketals include benzyl dimethyl ketal, and benzyl diethylketal.

Examples of the α-diketones include diacetyl, benzyl, camphorquinone,2,3-pentadione, 2,3-octadione, 9,10-phenanthrenequinone, 4,4′-oxybenzyl,and acenaphthenequinone. Particularly preferred is camphorquinone forits maximum absorption wavelength occurring in the visible light region.

Examples of the coumarin compounds include compounds mentioned in JP9(1997)-3109 A and JP 10(1998)-245525 A, such as 3,3′-carbonylbis(7-diethylaminocoumarin), 3-(4-methoxybenzoyl)coumarin,3-thienoylcoumarin, 3-benzoyl-5,7-dimethoxycoumarin,3-benzoyl-7-methoxycoumarin, 3-benzoyl-6-methoxycoumarin,3-benzoyl-8-methoxycoumarin, 3-benzoylcoumarin,7-methoxy-3-(p-nitrobenzoyl)coumarin, 3-(p-nitrobenzoyl)coumarin,3,5-carbonylbis(7-methoxycoumarin), 3-benzoyl-6-bromocoumarin,3,3′-carbonylbiscoumarin, 3-benzoyl-7-dimethylaminocoumarin,3-benzoylbenzo[f]coumarin, 3-carboxycoumarin,3-carboxy-7-methoxycoumarin, 3-ethoxycarbonyl-6-methoxycoumarin,3-ethoxycarbonyl-8-methoxycoumarin, 3-acetylbenzo[f]coumarin,3-benzoyl-6-nitrocoumarin, 3-benzoyl-7-diethylaminocoumarin,7-dimethylamino-3-(4-methoxybenzoyl)coumarin,7-diethylamino-3-(4-methoxybenzoyl)coumarin,7-diethylamino-3-(4-diethylamino)coumarin,7-methoxy-3-(4-methoxybenzoyl)coumarin,3-(4-nitrobenzoyl)benzo[f]coumarin,3-(4-ethoxycinnamoyl)-7-methoxycoumarin,3-(4-dimethylaminocinnamoyl)coumarin,3-(4-diphenylaminocinnamoyl)coumarin,3-[(3-dimethylbenzothiazol-2-ylidene)acetyl]coumarin,3-[(1-methylnaphtho[1,2-d]thiazol-2-ylidene)acetyl]coumarin,3,3′-carbonylbis(6-methoxycoumarin),3,3′-carbonylbis(7-acetoxycoumarin),3,3′-carbonylbis(7-dimethylaminocoumarin),3-(2-benzothiazolyl)-7-(diethylamino)coumarin,3-(2-benzothiazolyl)-7-(dibutylamino)coumarin,3-(2-benzoimidazolyl)-7-(diethylamino)coumarin,3-(2-benzothiazolyl)-7-(dioctylamino)coumarin,3-acetyl-7-(dimethylamino)coumarin,3,3′-carbonylbis(7-dibutylaminocoumarin),3,3′-carbonyl-7-diethylaminocoumarin-7′-bis(butoxyethyl)aminocoumarin,10-[3-[4-(dimethylamino)phenyl]-1-oxo-2-propenyl]-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-[1]benzopyrrano[6,7,8-ij]quinolizin-11-one,and10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-[1]benzopyrrano[6,7,8-ij]quinolizin-11-one.

Particularly preferred coumarin compounds are3,3′-carbonylbis(7-diethylaminocoumarin), and 3,3′-carbonylbis(7-dibutylaminocoumarin).

When the photopolymerization initiator is at least one selected from thegroup consisting of a (bis)acylphosphine oxide, an α-diketone, and acoumarin compound, a dental curable composition can be provided that hasdesirable photocurability both in the visible light region and the nearultraviolet region, and that shows sufficient photocurability regardlessof whether the light source used is a halogen lamp, a light emittingdiode (LED), or a xenon lamp.

The chemical polymerization initiators are preferably organic peroxides.The organic peroxides used as chemical polymerization initiators are notparticularly limited, and known organic peroxides may be used. Typicalexamples of organic peroxides include ketone peroxides, hydroperoxides,diacyl peroxides, dialkyl peroxides, peroxyketals, peroxyesters, andperoxydicarbonates.

Examples of the ketone peroxides include methyl ethyl ketone peroxide,methyl isobutyl ketone peroxide, methyl cyclohexanone peroxide, andcyclohexanone peroxide.

Examples of the hydroperoxides include2,5-dimethylhexane-2,5-dihydroperoxide, diisopropylbenzenehydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, and1,1,3,3-tetramethylbutyl hydroperoxide.

Examples of the diacyl peroxides include acetyl peroxide, isobutyrylperoxide, benzoyl peroxide, decanoyl peroxide, 3,5,5-trimethylhexanoylperoxide, 2,4-dichlorobenzoyl peroxide, and lauroyl peroxide.

Examples of the dialkyl peroxides include di-t-butyl peroxide, dicumylperoxide, t-butylcumyl peroxide,2,5-dimethyl-2,5-di(t-butylperoxy)hexane,1,3-bis(t-butylperoxyisopropyl)benzene, and2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne.

Examples of the peroxy ketals include1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)butane,2,2-bis(t-butylperoxy)octane, n-butyl 4,4-bis(t-butylperoxy) valerate.

Examples of the peroxyesters include α-cumyl peroxyneodecanoate, t-butylperoxyneodecanoate, t-butyl peroxypivalate, 2,2,4-trimethylpentylperoxy-2-ethylhexanoate, t-amyl peroxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, di-t-butyl peroxyisophthalate, di-t-butylperoxyhexahydroterephthalate, t-butyl peroxy-3,3,5-trimethylhexanoate,t-butyl peroxyacetate, t-butyl peroxybenzoate, and t-butyl peroxymaleicacid.

Examples of the peroxydicarbonates includedi-3-methoxyperoxydicarbonate, di(2-ethylhexyl)peroxydicarbonate,bis(4-t-butylcyclohexyl)peroxydicarbonate, diisopropylperoxydicarbonate,di-n-propylperoxydicarbonate, di(2-ethoxyethyl)peroxydicarbonate, anddiallylperoxydicarbonate.

From an overall balance of safety, storage stability, and radicalgenerating potential, preferred among these organic peroxides are diacylperoxides, particularly benzoyl peroxide.

The content of the polymerization initiator (C) in a dental curablecomposition of the present invention is not particularly limited.However, in view of considerations such as curability of the dentalcurable composition obtained, the content of the polymerizationinitiator (C) is preferably at least 0.001 parts by mass, morepreferably at least 0.01 parts by mass, even more preferably at least0.02 parts by mass, particularly preferably at least 0.1 parts by massrelative to total 100 parts by mass of the polymerizable monomer (A).The content of the polymerization initiator (C) is preferably at most 30parts by mass, more preferably at most 20 parts by mass, even morepreferably at most 15 parts by mass, particularly preferably at most 10parts by mass relative to total 100 parts by mass of the polymerizablemonomer (A) because the polymerization initiator (C) may precipitate outof the dental curable composition when its content is too high. Thecontent of the polymerization initiator (C) may be at most 5 parts bymass, or at most 2 parts by mass.

Fluorescent Agent (D)

A dental curable composition of the present invention comprises afluorescent agent (D). The fluorescent agent (D) comprises a 9- to11-membered benzo-fused heterocyclic compound containing two or moreheteroatoms (excluding benzoimidazole compounds). Examples of theheteroatoms include oxygen atoms, sulfur atoms, and nitrogen atoms.Preferred are oxygen atoms and nitrogen atoms. Preferably, at least oneof the two or more heteroatoms in the benzo-fused heterocyclic compoundis a nitrogen atom. The benzo-fused heterocyclic compound is preferablya fluorescent agent (D-1) representing a benzo-fused 6-memberedheterocyclic compound having two heteroatoms (hereinafter, also referredto simply as “fluorescent agent (D-1)”). The benzo-fused 6-memberedheterocyclic compound has a benzene ring fused with a 6-memberedheterocyclic ring having two heteroatoms. The fluorescent agent (D-1)may be, for example, a compound having a benzodiazinone skeleton, or acompound having a benzoxazinone skeleton. Examples of the compoundhaving a benzodiazinone skeleton include a compound (D-1a) having aquinazolinone skeleton, a compound (D-1b) having a cinnolinone skeleton,a compound (D-1c) having a phthalazinone skeleton, and a compound havinga quinoxalinone skeleton (D-1d). Preferred is a quinazolinone skeleton(D-1a). By the presence of the fluorescent agent (D-1), a dental curablecomposition and a cured product thereof can be provided that showfluorescence sufficient to provide a high aesthetic quality, and thatdesirably resist discoloration not only in the intraoral environment butunder accelerated heating conditions and under xenon light, withoutlosing fluorescence even under these conditions. Such a dental curablecomposition and a cured product can be suitably used in applicationssuch as dental composite resins and dental mill blanks. The exact reasonwhy a dental curable composition of the present invention and a curedproduct thereof can exhibit these desirable effects is not fullyunderstood. However, a likely explanation is the high stability of the9- to 11-membered benzo-fused heterocyclic ring skeleton containing twoor more heteroatoms, such as the benzodiazinone skeleton orbenzoxazinone skeleton.

Preferably, the fluorescent agent (D-1) is a compound having at leastone of a benzodiazinone skeleton (particularly preferably, aquinazolinone skeleton) and a benzoxazinone skeleton, more preferably acompound (D-1a) having a quinazolinone skeleton. The fluorescent agent(D-1) may have one benzodiazinone skeleton (particularly preferably, aquinazolinone skeleton) or one benzoxazinone skeleton, or may have morethan one benzodiazinone skeleton or more than one benzoxazinoneskeleton.

The benzodiazinone skeleton is represented by the following generalformula (5).

wherein X represents a 6-membered heterocyclic ring having two nitrogenatoms. The 6-membered heterocyclic ring has at least one oxo group (═O),and may be optionally substituted. Preferably, X is an aromaticheterocyclic ring, and has one —NH— in the ring. The number of oxogroups is not particularly limited, and may be 1 or 2, preferably 1.Specifically, X represents a moiety represented by any one of thefollowing formulae (X-1) to (X-5), preferably a moiety represented byformula (X-3) or (X-4), more preferably a moiety represented by formula(X-3).

The benzoxazinone skeleton is represented by the following generalformula (6).

where Y represents a 6-membered heterocyclic ring having one nitrogenatom and one oxygen atom. The 6-membered heterocyclic ring has at leastone oxo group, and may be optionally substituted. Y is preferably anaromatic heterocyclic ring. The number of oxo groups is not particularlylimited, and may be 1 or 2, preferably 1. Specifically, Y represents amoiety represented by any one of the following formulae (Y-1) to (Y-6),preferably a moiety represented by formula (Y-5) or (Y-6).

The benzodiazinone skeleton (particularly preferably, a quinazolinoneskeleton) and the benzoxazinone skeleton may or may not have asubstituent.

Examples of the substituent include a hydroxyl group, a thiol group, anitro group, a halogen atom, an alkyl group having 1 to 10 carbon atoms,an alkenyl group (such as a vinyl group or an allyl group), an alkoxygroup having 1 to 10 carbon atoms, an aromatic group (such as a phenylgroup, a naphthyl group, or a styryl group), a C1 to C10 halogenatedalkyl group substituted with a halogen atom, an acyl group (such as anacetyl group), an amino group, an alkylamino group (such as amethylamino group), a dialkylamino group (such as a dimethylaminogroup), an aminoalkyl group (such as an aminoethyl group), a carboxygroup, an alkoxycarbonyl group (such as a methoxycarbonyl group), analkoxycarbonylalkyl group (such as a methoxycarbonylmethyl group), analkyloxyalkyl group (such as a methyloxymethyl group), an alkylthioalkylgroup (such as a methylthiomethyl group), an aminoalkylaminoalkyl group(such as an aminomethylaminomethyl group), an alkylcarbonyloxy group(such as a methylcarbonyloxy group), an arylalkoxyalkoxyalkyl group(such as a benzyloxyethoxyethyl group), a hydroxyalkoxyalkyl group (suchas a hydroxyethoxymethyl group), an arylalkoxyalkyl group (such as abenzyloxymethyl group), a quaternary ammonio group (such as atrimethylammonio group), a cycloalkyl group (such as a cyclopropylgroup), an alkoxycarbonyl group (such as a tert-butoxycarbonyl group), asubstituted sulfonyl group (such as a p-toluenesulfonyl group), asubstituted sulfoneamide group (such as a benzenesulfoneamide group), anacryloyl group (such as a benzoyl group), and an oxygen atom (═O). Thenumber of substituents may be 1 to 10, 1 to 6, or 1 to 3. Thesubstituents may be combined with each other. For example, thesubstituent may be substituted with any of the above substituents, ormay have no substituent.

The fluorescent agent (D-1) is preferably a compound having a moietyrepresented by the following general formula (1) or (2).

wherein R¹ in general formulae (1) and (2) is an oxygen atom or —NH—,and R² in general formulae (1) and (2) represents an optionallysubstituted aromatic group.

Examples of the aromatic group represented by R² include:

aryl groups such as a phenyl group, a biphenylyl group, a terphenylylgroup, a styryl group, a naphthyl group, an anthryl group, anacenaphthenyl group, a fluorenyl group, a phenanthryl group, and anindenyl group;

aralkyl groups such as a benzyl group, a phenethyl group, a1-phenylethyl group, a 2-phenylpropyl group, a 3-phenylpropyl group, aphenylbutyl group, a 1-methyl-3-phenylpropyl group, a naphthylmethylgroup, a naphthylethyl group, a naphthylpropyl group, and anaphthylbutyl group; and

heteroaromatic rings such as a pyrenyl group, a pyrimidyl group, afuranyl group, a pyronyl group, a thienyl group, a quinolyl group, abenzofuranyl group, a benzothiophenyl group, an indolyl group, acarbazolyl group, a carbolyl group, a benzoxazolyl group, a quinoxalylgroup, a benzoimidazolyl group, a pyrazolyl group, a dibenzofuranylgroup, and a dibenzothiophenyl group.

In view of fluorescence and durability, preferred are a phenyl group, anaphthyl group, and a styryl group.

The aromatic group represented by R² may or may not have a substituent.Examples of the substituent include the substituents exemplified assubstituents of the benzodiazinone skeleton and benzoxazinone skeleton.In view of fluorescence and durability, the substituent is preferably ahydroxyl group, a halogen atom, an alkyl group having 1 to 3 carbonatoms, a C1 to C3 halogenated alkyl group substituted with a halogenatom, a dimethylamino group, a carboxy group, or a benzenesulfoneamidegroup. The number of substituents may be 1 to 20, 1 to 10, 1 to 6, or 1to 3. The substituents may be combined with each other. For example, thesubstituent may be substituted with any of the above substituents, ormay have no substituent.

In view of fluorescence and durability, the fluorescent agent (D-1) ispreferably 2-(2-hydroxyphenyl)-4(1H)-quinazolinone,2-(2-hydroxyphenyl)-4H-3,1-benzoxazin-4-one,N-[2-(4(1H)-quinazolinon-2-yl)phenyl]benzenesulfoneamide,N-[2-(4-oxo-1,3-benzoxazin-2-yl)phenyl]benzenesulfoneamide,7-dimethylamino-3-[2-[4-(trifluoromethyl)phenyl]ethenyl]-2H-1,4-benzoxazin-2-one,7-dimethylamino-3-[2-[2,3,4,5,6-pentafluorophenyl]ethenyl]-2H-1,4-benzoxazin-2-one,or7-dimethylamino-3-[2-[2,4-bis(trifluoromethyl)phenyl]ethenyl]-2H-1,4-benzoxazin-2-one,more preferably 2-(2-hydroxyphenyl)-4(1H)-quinazolinone, orN-[2-(4-oxo-1,3-benzoxazin-2-yl)phenyl]benzenesulfoneamide.

The content of the fluorescent agent (D-1) in a dental curablecomposition of the present invention is not particularly limited.However, in order for the dental curable composition to exhibitsufficient fluorescence, the content of the fluorescent agent (D-1) ispreferably at least 0.0001 parts by mass, more preferably at least0.0002 parts by mass, even more preferably at least 0.0005 parts bymass, particularly preferably at least 0.001 parts by mass relative tototal 100 parts by mass of polymerizable monomer (A) and inorganicfiller (B), and is preferably at least 0.0005 parts by mass, morepreferably at least 0.001 parts by mass, even more preferably at least0.002 parts by mass, particularly preferably at least 0.005 parts bymass relative to total 100 parts by mass of polymerizable monomer (A).Because an excessively high content of fluorescent agent (D-1) may harmthe aesthetics of the dental curable composition, the content of thefluorescent agent (D-1) is preferably at most 3 parts by mass, morepreferably at most 1 part by mass, even more preferably at most 0.5parts by mass, particularly preferably at most 0.1 parts by massrelative to total 100 parts by mass of polymerizable monomer (A) andinorganic filler (B), and is preferably at most 5 parts by mass, morepreferably at most 1 part by mass, even more preferably at most 0.5parts by mass, particularly preferably at most 0.2 parts by massrelative to total 100 parts by mass of polymerizable monomer (A). Thefluorescent agent (D-1) may be used alone, or two or more thereof may beused in combination. By using two or more fluorescent agents (D-1) incombination, the color of the fluorescence of a cured product of adental curable composition of the present invention can be adjusted asdesired by varying the fractions of the fluorescent agents (D-1). Thatis, a highly aesthetic dental curable composition can be provided thatcan exhibit fluorescence even closer to that of natural teeth.

In addition to the fluorescent agent (D-1), a dental curable compositionof the present invention preferably comprises a fluorescent agent(D-2)—another fluorescent agent (D) representing a benzo-fused5-membered heterocyclic compound having one nitrogen atom and one oxygenatom. The benzo-fused 5-membered heterocyclic compound has a benzenering fused with a 5-membered heterocyclic ring having one nitrogen atomand one oxygen atom. Examples of the fluorescent agent (D-2) include afluorescent agent (D-2a), which is a compound having a benzoxazoleskeleton (hereinafter, also referred to simply as “fluorescent agent(D-2a)”), and a fluorescent agent (D-2b), which is a compound having abenzisoxazole skeleton. Particularly preferably, the fluorescent agent(D-2) is a fluorescent agent (D-2a), a compound having a benzoxazoleskeleton. By using the fluorescent agent (D-1) with the fluorescentagent (D-2), the color of the fluorescence of a cured product of adental curable composition of the present invention can be adjusted asdesired by varying the fractions of these fluorescent agents. That is, ahighly aesthetic dental curable composition can be provided that canexhibit fluorescence even closer to that of natural teeth, and that hasdesirable discoloration resistance and fluorescence durability.

The fluorescent agent (D-2a) means a compound having a benzoxazoleskeleton, as represented by formula (7) below. The fluorescent agent(D-2a) may have a plurality of benzoxazole skeletons. The benzoxazoleskeleton may or may not have a substituent. Examples of the substituentinclude the substituents exemplified as substituents of thequinazolinone skeleton and benzoxazinone skeleton. In view offluorescence and durability, the substituent is preferably a hydroxylgroup, a halogen atom, or an alkyl group having 1 to 3 carbon atoms. Thenumber of substituents may be 1 to 20, 1 to 10, 1 to 6, or 1 to 3. Thesubstituent may or may not have a substituent.

In view of a color of fluorescence and durability, the fluorescent agent(D-2a) is preferably a compound having a moiety represented by thefollowing general formula (3).

wherein R³ represents an optionally substituted aromatic group, or anoptionally substituted vinylene group.

Examples of the aromatic group represented by R³ include divalent groupsof the groups exemplified as aromatic groups represented by R² of thegeneral formulae (1) and (2). Preferred are a phenylene group, anaphthylene group, and a thienylene group.

Compounds represented by the general formula (3) may or may not have asubstituent. The substituent may be, for example, any of thesubstituents exemplified as substituents of the benzoxazole skeleton.

In view of fluorescence and durability, the fluorescent agent (D-2a) asa compound having a benzoxazole skeleton is preferably1,4-bis(2-benzoxazolyl)naphthalene, 4,4′-bis(2-benzoxazolyl)stilbene,1,2-bis(5-methylbenzoxazol-2-yl)ethene,4,4′-bis(5-methyl-2-benzoxazolyl)stilbene,4-(2-benzoxazolyl)-4′-(5-methyl-2-benzoxazolyl)stilbene,2,5-bis(benzoxazol-2-yl)thiophene, or2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene.

The content of the fluorescent agent (D-2) in a dental curablecomposition of the present invention is not particularly limited.However, in order for the dental curable composition to exhibitsufficient fluorescence, the content of fluorescent agent (D-2) ispreferably at least 0.0001 parts by mass, more preferably at least0.0002 parts by mass, even more preferably at least 0.0005 parts bymass, particularly preferably at least 0.001 parts by mass relative tototal 100 parts by mass of polymerizable monomer (A) and inorganicfiller (B). In order for the dental curable composition to exhibitsufficient fluorescence, the content of fluorescent agent (D-2) ispreferably at least 0.0005 parts by mass, more preferably at least 0.001parts by mass, even more preferably at least 0.002 parts by mass,particularly preferably at least 0.005 parts by mass relative to total100 parts by mass of polymerizable monomer (A). Because an excessivelyhigh content of fluorescent agent (D-2) may harm the aesthetics of thedental curable composition, the content of fluorescent agent (D-2) ispreferably at most 3 parts by mass, more preferably at most 1 part bymass, even more preferably at most 0.5 parts by mass, particularlypreferably at most 0.1 parts by mass relative to total 100 parts by massof polymerizable monomer (A) and inorganic filler (B). Forconsiderations such as possible impairment of the aesthetic quality ofthe dental curable composition, the content of fluorescent agent (D-2)is preferably at most 5 parts by mass, more preferably at most 1 part bymass, even more preferably at most 0.5 parts by mass, particularlypreferably at most 0.2 parts by mass relative to total 100 parts by massof polymerizable monomer (A). The fluorescent agent (D-2) may be usedalone, or two or more thereof may be used in combination. A certainembodiment of a dental curable composition of the present invention is,for example, a dental curable composition that comprises a polymerizablemonomer (A), an inorganic filler (B), a polymerization initiator (C),and a fluorescent agent (D), wherein the fluorescent agent (D) comprisesa 9- to 11-membered benzo-fused heterocyclic compound containing two ormore heteroatoms (excluding benzoimidazole compounds), and the 9- to11-membered benzo-fused heterocyclic compound containing two or moreheteroatoms contains no fluorescent agent (D-1) but contains afluorescent agent (D-2).

A dental curable composition of the present invention may comprise afluorescent agent (D-3) containing a phthalic acid ester, provided thatthe present invention can exhibit its effects. The fluorescent agent(D-3) containing a phthalic acid ester is different from the fluorescentagents (D-1) and (D-2). The fluorescent agent (D-3) containing aphthalic acid ester is represented by the following general formula (8).

wherein R¹⁰ and R¹¹ are each independently an alkyl group, R¹² is ahydrogen atom, an amino group, or a hydroxyl group, and R¹³ is an aminogroup or a hydroxyl group.

The alkyl group is preferably an alkyl group having 1 to 3 carbon atoms,such as methyl, ethyl, n-propyl, or i-propyl, particularly preferably analkyl group having 1 to 2 carbon atoms.

Because the presence of the fluorescent agent (D-3) in a dental curablecomposition of the present invention can cause a change in the shade ofthe dental curable composition (yellowing), the content of fluorescentagent (D-3) is preferably at most 0.5 parts by mass, more preferably atmost 0.1 parts by mass, even more preferably at most 0.01 parts by mass,particularly preferably zero (fluorescent agent (D-3) is absent)relative to total 100 parts by mass of polymerizable monomer (A) andinorganic filler (B). Because the presence of fluorescent agent (D-3) ina dental curable composition of the present invention can cause a changein the shade of the dental curable composition (yellowing), the contentof fluorescent agent (D-3) is preferably at most 0.1 parts by mass, morepreferably at most 0.01 parts by mass, even more preferably at most0.001 parts by mass, particularly preferably zero (fluorescent agent(D-3) is absent) relative to total 100 parts by mass of polymerizablemonomer (A). The fluorescent agent (D-3) may be used alone, or two ormore thereof may be used in combination. A preferred embodiment of thepresent invention is, for example, a dental curable compositioncomprising a fluorescent agent (D) with no fluorescent agent (D-3).

The fluorescent agent (D) in a dental curable composition of the presentinvention may additionally contain a fluorescent agent (D-4) other thanthe fluorescent agents (D-1), (D-2), and (D-3).

The fluorescent agent (D-4) may be selected from fluorescent agentscommonly used in industry, preferably those used in dentistry. Thefluorescent agent (D-4) can be broadly divided into organic fluorescentagents and inorganic fluorescent agents. The fluorescent agent (D-4) maybe used alone, or two or more thereof may be used in combination.

Examples of the organic fluorescent agents include coumarin fluorescentagents, naphthalimide fluorescent agents, xanthene fluorescent agents,thioxanthene fluorescent agents, naphtholactam fluorescent agents,thiazine fluorescent agents, oxazole fluorescent agents, furanfluorescent agents, benzofuran fluorescent agents, pyrazolinefluorescent agents, stilbene fluorescent agents, distyrylbenzenefluorescent agents, distyrylbiphenyl fluorescent agents, benzoimidazolecompounds, 1,3,5-triazin-2-yl derivatives, aryl benzoguanaminefluorescent agents, and polycyclic aromatic hydrocarbon fluorescentagents.

Examples of the inorganic fluorescent agents include Y₂SiO₅:Ce,Y₂SiO₅:Tb, (Y,Gd,Eu)BO₃, Y₂O₃:Eu, YAG:Ce, ZnGa₂O₄:Zn, BaMgAl₁₀O₁₇:Eu,BaMgAl₁₀O₁₇:Eu, (SrCaBaMg)₅(PO₄)₃Cl:Eu, Zn₂SiO₄:Mn, BaMg₂Al₁₆O₂₇:Eu,BaMg₂Al₁₆O₂₇:Eu,Mn, BaMg₂Al₁₆O₂₇:Mn, LaPO₄:Ce, LaPO₄:Tb, LaPO₄:Ce,Tb,Y₃Al₅O₁₂:Ce, and Y₂O₂S:Eu. In view of a color of fluorescence, Y₂SiO₅:Ceis preferred.

Polymerization Accelerator (E)

A dental curable composition of the present invention may furthercomprise a polymerization accelerator (E). Examples of thepolymerization accelerator include amines, sulfinic acids and saltsthereof, derivatives of barbituric acid, borate compounds, triazinecompounds, copper compounds, tin compounds, vanadium compounds, halogencompounds, aldehydes, thiol compounds, sulfites, bisulfites, andthiourea compounds. The polymerization accelerator (E) may be usedalone, or two or more thereof may be used in combination. A certainpreferred embodiment may be a dental curable composition in which thepolymerization initiator (C) comprises a photopolymerization initiator,and the dental curable composition additionally comprises apolymerization accelerator (E) that is a tertiary amine. The tertiaryamine is preferably a tertiary aromatic amine. The dental curablecomposition of such a preferred embodiment is more suited as a dentalcomposite resin.

The amines can be classified into aliphatic amines and aromatic amines.Examples of the aliphatic amines include primary aliphatic amines suchas n-butylamine, n-hexylamine, and n-octylamine; secondary aliphaticamines such as diisopropylamine, dibutylamine, and N-methylethanolamine;and tertiary aliphatic amines such as N-methyldiethanolamine,N-ethyldiethanolamine, N-n-butyldiethanolamine, N-lauryldiethanolamine,2-(dimethylamino)ethyl methacrylate, N-methyldiethanolaminedimethacrylate, N-ethyldiethanolamine dimethacrylate, triethanolaminemonomethacrylate, triethanolamine dimethacrylate, triethanolaminetrimethacrylate, triethanolamine, trimethylamine, triethylamine, andtributylamine. In view of curability and storage stability of the dentalcurable composition, preferred for use are tertiary aliphatic amines,more preferably N-methyldiethanolamine and triethanolamine.

Examples of the aromatic amines includeN,N-bis(2-hydroxyethyl)-3,5-dimethylaniline,N,N-bis(2-hydroxyethyl)-p-toluidine,N,N-bis(2-hydroxyethyl)-3,4-dimethylaniline,N,N-bis(2-hydroxyethyl)-4-ethylaniline,N,N-bis(2-hydroxyethyl)-4-isopropylaniline,N,N-bis(2-hydroxyethyl)-4-t-butylaniline,N,N-bis(2-hydroxyethyl)-3,5-di-isopropylaniline,N,N-bis(2-hydroxyethyl)-3,5-di-t-butylaniline, N,N-dimethylaniline,N,N-dimethyl-p-toluidine, N,N-dimethyl-m-toluidine,N,N-diethyl-p-toluidine, N,N-dimethyl-3,5-dimethylaniline,N,N-dimethyl-3,4-dimethylaniline, N,N-dimethyl-4-ethylaniline,N,N-dimethyl-4-isopropylaniline, N,N-dimethyl-4-t-butylaniline,N,N-dimethyl-3,5-di-t-butylaniline, ethyl 4-(N,N-dimethylamino)benzoate,methyl 4-(N,N-dimethylamino)benzoate, 2-butoxyethyl4-(N,N-dimethylamino)benzoate, 2-(methacryloyloxy)ethyl4-(N,N-dimethylamino)benzoate, 4-(N,N-dimethylamino)benzophenone, andbutyl 4-(N,N-dimethylamino)benzoate. In view of the ability to impartdesirable curability to the dental curable composition, preferred foruse is at least one selected from the group consisting ofN,N-bis(2-hydroxyethyl)-p-toluidine, ethyl4-(N,N-dimethylamino)benzoate, 2-butoxyethyl4-(N,N-dimethylamino)benzoate, and 4-(N,N-dimethylamino)benzophenone.

Examples of the sulfinic acids and salts thereof includep-toluenesulfinic acid, sodium p-toluenesulfinate, potassiump-toluenesulfinate, lithium p-toluenesulfinate, calciump-toluenesulfinate, benzenesulfinic acid, sodium benzenesulfinate,potassium benzenesulfinate, lithium benzenesulfinate, calciumbenzenesulfinate, 2,4,6-trimethylbenzenesulfinic acid, sodium2,4,6-trimethylbenzenesulfinate, potassium2,4,6-trimethylbenzenesulfinate, lithium2,4,6-trimethylbenzenesulfinate, calcium2,4,6-trimethylbenzenesulfinate, 2,4,6-triethylbenzenesulfinic acid,sodium 2,4,6-triethylbenzenesulfinate, potassium2,4,6-triethylbenzenesulfinate, lithium 2,4,6-triethylbenzenesulfinate,calcium 2,4,6-triethylbenzenesulfinate,2,4,6-triisopropylbenzenesulfinic acid, sodium2,4,6-triisopropylbenzenesulfinate, potassium2,4,6-triisopropylbenzenesulfinate, lithium2,4,6-triisopropylbenzenesulfinate, and calcium2,4,6-triisopropylbenzenesulfinate. Particularly preferred are sodiumbenzenesulfinate, sodium p-toluenesulfinate, and sodium2,4,6-triisopropylbenzenesulfinate.

Examples of the derivatives of barbituric acid include barbituric acid,1,3-dimethylbarbituric acid, 1,3-diphenylbarbituric acid,1,5-dimethylbarbituric acid, 5-butylbarbituric acid, 5-ethylbarbituricacid, 5-isopropylbarbituric acid, 5-cyclohexylbarbituric acid,1,3,5-trimethylbarbituric acid, 1,3-dimethyl-5-ethylbarbituric acid,1,3-dimethyl-5-n-butylbarbituric acid, 1,3-dimethyl-5-isobutylbarbituricacid, 1,3-dimethyl-5-cyclopentylbarbituric acid,1,3-dimethyl-5-cyclohexylbarbituric acid,1,3-dimethyl-5-phenylbarbituric acid, 1-cyclohexyl-1-ethylbarbituricacid, 1-benzyl-5-phenylbarbituric acid, 5-methylbarbituric acid,5-propylbarbituric acid, 1,5-diethylbarbituric acid,1-ethyl-5-methylbarbituric acid, 1-ethyl-5-isobutylbarbituric acid,1,3-diethyl-5-butylbarbituric acid, 1-cyclohexyl-5-methylbarbituricacid, 1-cyclohexyl-5-ethylbarbituric acid,1-cyclohexyl-5-octylbarbituric acid, 1-cyclohexyl-5-hexylbarbituricacid, 5-butyl-1-cyclohexylbarbituric acid, 1-benzyl-5-phenylbarbituricacid, thiobarbituric acid, and salts of these (particularly preferredare alkali metal salts or alkali earth metal salts). Examples of thesalts of barbituric acid include sodium 5-butylbarbiturate, sodium1,3,5-trimethylbarbiturate, and sodium 1-cyclohexyl-5-ethylbarbiturate.

Particularly preferred as derivatives of barbituric acid are, forexample, 5-butylbarbituric acid, 1,3,5-trimethylbarbituric acid,1-cyclohexyl-5-ethylbarbituric acid, 1-benzyl-5-phenylbarbituric acid,and sodium salts of these barbituric acids.

The borate compounds are preferably arylborate compounds. Examples ofthe arylborate compounds include borate compounds having 1 to 4 arylgroups per molecule. In view of storage stability, preferred asarylborate compounds are borate compounds having 3 or 4 aryl groups permolecule. Examples of the borate compounds having 3 aryl groups permolecule include monoalkyl triphenylboron, monoalkyltri(p-chlorophenyl)boron, monoalkyl tri(p-fluorophenyl)boron, monoalkyltri[3,5-bis(trifluoromethyl)phenyl]boron, monoalkyltri[3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxy-2-propyl)phenyl]boron,monoalkyl tri(p-nitrophenyl)boron, monoalkyl tri(m-nitrophenyl)boron,monoalkyl tri(p-butylphenyl)boron, monoalkyl tri(m-butylphenyl)boron,monoalkyl tri(p-butyloxyphenyl)boron, monoalkyltri(m-butyloxyphenyl)boron, monoalkyl tri(p-octyloxyphenyl)boron,monoalkyl tri(m-octyloxyphenyl)boron (the alkyl groups in these examplecompounds are, for example, n-butyl, n-octyl, or n-dodecyl), and saltsof these (e.g., sodium salts, lithium salts, potassium salts, magnesiumsalts, tetrabutylammonium salts, tetramethylammonium salts,tetraethylammonium salts, methylpyridinium salts, ethylpyridinium salts,butylpyridinium salts, methylquinolinium salts, ethylquinolinium salts,and butylquinolinium salts).

Examples of the borate compounds having 4 aryl groups per moleculeinclude tetraphenylboron, tetrakis(p-chlorophenyl)boron,tetrakis(p-fluorophenyl)boron,tetrakis[3,5-bis(trifluoromethyl)phenyl]boron,tetrakis[3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxy-2-propyl)phenyl]boron,tetrakis(p-nitrophenyl)boron, tetrakis(m-nitrophenyl)boron,tetrakis(p-butylphenyl)boron, tetrakis(m-butylphenyl)boron,tetrakis(p-butyloxyphenyl)boron, tetrakis(m-butyloxyphenyl)boron,tetrakis(p-octyloxyphenyl)boron, tetrakis(m-octyloxyphenyl)boron,(p-fluorophenyl)triphenylboron,[3,5-bis(trifluoromethyl)phenyl]triphenylboron,(p-nitrophenyl)triphenylboron, (m-butyloxyphenyl)triphenylboron,(p-butyloxyphenyl)triphenylboron, (m-octyloxyphenyl)triphenylboron,(p-octyloxyphenyl)triphenylboron, and salts of these (e.g., sodiumsalts, lithium salts, potassium salts, magnesium salts,tetrabutylammonium salts, tetramethylammonium salts, tetraethylammoniumsalts, methylpyridinium salts, ethylpyridinium salts, butylpyridiniumsalts, methylquinolinium salts, ethylquinolinium salts, andbutylquinolinium salts).

Examples of the triazine compounds include2,4,6-tris(trichloromethyl)-s-triazine,2,4,6-tris(tribromomethyl)-s-triazine,2-methyl-4,6-bis(trichloromethyl)-s-triazine,2-methyl-4,6-bis(tribromomethyl)-s-triazine,2-phenyl-4,6-bis(trichloromethyl)-s-triazine,2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine,2-(p-methylthiophenyl)-4,6-bis(trichloromethyl)-s-triazine,2-(p-chlorophenyl)-4,6-bis(trichloromethyl)-s-triazine,2-(2,4-dichlorophenyl)-4,6-bis(trichloromethyl)-s-triazine,2-(p-bromophenyl)-4,6-bis(trichloromethyl)-s-triazine,2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine,2-n-propyl-4,6-bis(trichloromethyl)-s-triazine,2-(α,α,β-trichloroethyl)-4,6-bis(trichloromethyl)-s-triazine,2-styryl-4,6-bis(trichloromethyl)-s-triazine,2-[2-(p-methoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-s-triazine,2-[2-(o-methoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-s-triazine,2-[2-(p-butoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-s-triazine,2-[2-(3,4-dimethoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-s-triazine,2-[2-(3,4,5-trimethoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-s-triazine,2-(1-naphthyl)-4,6-bis(trichloromethyl)-s-triazine,2-(4-biphenylyl)-4,6-bis(trichloromethyl)-s-triazine,2-[2-{N,N-bis(2-hydroxyethyl)amino}ethoxy]-4,6-bis(trichloromethyl)-s-triazine,2-[2-{N-hydroxyethyl-N-ethylamino}ethoxy]-4,6-bis(trichloromethyl)-s-triazine,2-[2-{N-hydroxyethyl-N-methylamino}ethoxy]-4,6-bis(trichloromethyl)-s-triazine,and 2-[2-{N,N-diallylamino}ethoxy]-4,6-bis(trichloromethyl)-s-triazine.

In view of polymerization activity, particularly preferred as a triazinecompound is 2,4,6-tris(trichloromethyl)-s-triazine. In view of storagestability, particularly preferred are2-phenyl-4,6-bis(trichloromethyl)-s-triazine,2-(p-chlorophenyl)-4,6-bis(trichloromethyl)-s-triazine, and2-(4-biphenylyl)-4,6-bis(trichloromethyl)-s-triazine. The triazinecompounds may be used alone, or two or more thereof may be used incombination.

Preferred for use as copper compounds are, for example, copperacetylacetonate, copper(II) acetate, copper oleate, copper(II) chloride,and copper(II) bromide.

Examples of the tin compounds include di-n-butyltin dimaleate,di-n-octyltin dimaleate, di-n-octyltin dilaurate, and di-n-butyltindilaurate. Preferred as tin compounds are di-n-octyltin dilaurate anddi-n-butyltin dilaurate.

The vanadium compounds are preferably vanadium compounds with valencesof IV and/or V. Examples of vanadium compounds with valences of IVand/or V include compounds mentioned in JP 2003-96122 A, for example,such as vanadium(IV) oxide, vanadium(IV)oxy acetylacetonate, vanadyloxalate, vanadyl sulfate, vanadium(IV)oxobis(1-phenyl-1,3-butanedionate), bis(maltolato)oxovanadium(IV),vanadium(V) oxide, sodium metavanadate, and ammonium metavanadate.

Preferred for use as halogen compounds are, for example,dilauryldimethylammonium chloride, lauryldimethylbenzylammoniumchloride, benzyltrimethylammonium chloride, tetramethylammoniumchloride, benzyldimethylcetylammonium chloride, anddilauryldimethylammonium bromide.

Examples of the aldehydes include terephthalaldehyde, and derivatives ofbenzaldehyde. Examples of derivatives of benzaldehyde includedimethylaminobenzaldehyde, p-methoxybenzaldehyde, p-ethoxybenzaldehyde,and p-n-octyloxybenzaldehyde. In view of curability, preferred for useis p-n-octyloxybenzaldehyde.

Examples of the thiol compounds include3-mercaptopropyltrimethoxysilane, 2-mercaptobenzoxazole, decanethiol,and thiobenzoic acid.

Examples of the sulfites include sodium sulfite, potassium sulfite,calcium sulfite, and ammonium sulfite.

Examples of the bisulfites include sodium bisulfite and potassiumbisulfite.

Examples of the thiourea compounds include 1-(2-pyridyl)-2-thiourea,thiourea, methylthiourea, ethylthiourea, N,N′-dimethylthiourea,N,N′-diethylthiourea, N,N′-di-n-propylthiourea,N,N′-dicyclohexylthiourea, trimethylthiourea, triethylthiourea,tri-n-propylthiourea, tricyclohexylthiourea, tetramethylthiourea,tetraethylthiourea, tetra-n-propylthiourea, and tetracyclohexylthiourea.

When the polymerization accelerator (E) is present in a dental curablecomposition of the present invention, the content of polymerizationaccelerator (E) is not particularly limited. However, in view ofconsiderations such as curability of the dental curable compositionobtained, the content of polymerization accelerator (E) is preferably atleast 0.001 parts by mass, more preferably at least 0.01 parts by mass,even more preferably at least 0.02 parts by mass relative to total 100parts by mass of polymerizable monomer (A). The content ofpolymerization accelerator (E) may be at least 0.03 parts by mass, atleast 0.05 parts by mass, or at least 0.1 parts by mass. Forconsiderations such as possible precipitation of polymerizationaccelerator (E) as might occur in the dental curable composition whenthe content of polymerization accelerator (E) is too high, the contentof polymerization accelerator (E) is preferably at most 30 parts bymass, more preferably at most 20 parts by mass, even more preferably atmost 10 parts by mass, particularly preferably at most 5 parts by massrelative to total 100 parts by mass of polymerizable monomer (A). Thecontent of polymerization accelerator (E) may be at most 2 parts bymass, at most 1 part by mass, or at most 0.5 parts by mass.

Additive (F)

A dental curable composition of the present invention may optionallycomprise an additive (F), for example, such as a polymerizationinhibitor, a ultraviolet absorber, an antioxidant, an antimicrobialagent, a dispersant, a pH adjuster, a pigment, or a dye, other than thepolymerizable monomer (A), inorganic filler (B), polymerizationinitiator (C), fluorescent agent (D), and polymerization accelerator (E)described above. The additive (F) may be used alone, or two or morethereof may be used in combination.

Examples of the polymerization inhibitor include3,5-di-t-butyl-4-hydroxytoluene, hydroquinone, dibutyl hydroquinone,dibutyl hydroquinone monomethyl ether, hydroquinone monomethyl ether,and 2,6-di-t-butylphenol. These may be used alone, or two or morethereof may be used in combination. Examples of the ultraviolet absorberinclude benzotriazole compounds such as2-(2-hydroxyphenyl)benzotriazole,2-(2-hydroxy-5-methylphenyl)benzotriazole,2-(2-hydroxy-5-ethylphenyl)benzotriazole,2-(2-hydroxy-5-propylphenyl)benzotriazole,2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, and2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chloro-2H-benzotriazole(Tinuvin 326); and benzoimidazole compounds. These may be used alone, ortwo or more thereof may be used in combination.

Method of Production of Dental Curable Composition

A method of production of a dental curable composition of the presentinvention is not particularly limited, and a dental curable compositionof the present invention can be obtained by combining the components inpredetermined amounts. The components may be combined in any order, atonce or in two or more separate portions. Optionally, the components maybe mixed or kneaded, or may be subjected to degassing, for example,vacuum degassing. The resultant dental curable composition may becharged into a single container (e.g., a syringe) to prepare a one-pack(one-paste) type dental curable composition.

Uses

A dental curable composition of the present invention and a curedproduct thereof are not limited to particular uses, and may be used as avariety of dental materials. Specifically, a dental curable compositionof the present invention can be suitably used as, for example, a dentalcomposite resin (for example, a composite resin for filling cavities, acomposite resin for abutment construction, a composite resin for dentalcaps), a denture base resin, a denture base liner, an impressionmaterial, a luting material (for example, a resin cement, a resin-addedglass ionomer cement), a dental bonding agent (for example, anorthodontics adhesive, an adhesive for application to cavities), a toothfissure sealant, a resin block for CAD/CAM, a temporary crown, or anartificial teeth material. Because of high aesthetic quality anddesirable mechanical strength, a dental curable composition of thepresent invention is particularly suited for dental composite resins,and resin blocks for CAD/CAM.

The present invention encompasses embodiments combining the foregoingfeatures, provided that such combinations made in various forms withinthe technical idea of the present invention can produce the effects ofthe present invention.

EXAMPLES

The following describes the present invention in greater detail by wayof Examples and Comparative Examples. It is to be noted, however, thatthe present invention is not limited to the following Examples. Thefollowing summarizes details of Examples, including the test methods andmaterials used in Examples.

Test Methods

Average Particle Diameter of Filler

The fillers below were measured for average particle diameter by volumewith a laser diffraction particle size distribution analyzer (SALD-2300,manufactured by Shimadzu Corporation), using ethanol as dispersionmedium (N=1). A scanning electron microscope (SU3500, manufactured byHitachi High-Technologies Corporation) was also used instead for themeasurement of average particle diameter.

Specific Surface Area of Inorganic Filler

The inorganic filler obtained in each Production Example was washed at450° C. for 4 hours in an electric furnace, and, after degassing withvacuum at 100° C. for 2 hours, the specific surface area of theinorganic filler was measured by the BET method with a specific surfacearea measurement device (BELSORP-mini II, manufactured by MicrotracBELCorp.), using nitrogen as adsorbate gas and at a measurement temperatureof 77 K (N=1). For the measurement, a multi-point BET analysis wasadopted by taking 5 points on the adsorption isotherm in the pressure(P/P₀) range of 0.05 to 0.3, where P is the adsorbate equilibriumpressure (kPa), and P₀ is the saturated vapor pressure (kPa)

Mechanical Strength (Flexural Strength): Dental Composite Resin

The dental curable compositions produced in Examples and ComparativeExamples were degassed in vacuum, and each was charged into astainless-steel mold (dimensions: 2 mm×2 mm×25 mm). With the dentalcurable composition being pressed between glass slides from top andbottom, light was applied through the glass slides from both sides tocure the dental curable composition. Here, light was applied at 5 pointseach side, 10 seconds at each point, using a dental visible-lightphotoirradiator (PenCure 2000, manufactured by J. Morita Corp.). A totalof five cured products were prepared as specimens for each Example andComparative Example. The cured product was stored in 37° C. distilledwater for 24 hours after being taken out of the mold. For measurements,the cured product specimens were measured for three-point flexuralstrength according to JIS T 6514:2015 and ISO 4049:2019 at a span lengthof 20 mm and a crosshead speed of 1 mm/min, using a universal testingmachine (AG-I, 100 kN, manufactured by Shimadzu Corporation under thistrade name). From the measured values, a mean value was calculated foreach specimen to find the flexural strength. The preferred flexuralstrength is 100 MPa or more, more preferably 110 MPa or more, even morepreferably 120 MPa or more.

Mechanical Strength (Flexural Strength): Dental Mill Blank

A total of 10 specimens (each measuring 1.2 mm×4 mm×14 mm) were preparedfrom a cured product of the dental curable composition produced in eachExample and Comparative Example, using a diamond cutter. After beingimmersed in 37° C. distilled water for 24 hours, the specimens weremeasured for three-point flexural strength according to JDMAS 245:2017(Resin Material for CAD/CAM Crowns by Milling and Machining) at a spanlength of 12 mm and a crosshead speed of 1 mm/min, using a universaltesting machine (AG-I, 100 kN, manufactured by Shimadzu Corporationunder this trade name). From the measured values, a mean value wascalculated for each specimen to find the flexural strength (N=10). Thepreferred flexural strength is 150 MPa or more, more preferably 165 MPaor more, even more preferably 180 MPa or more.

Shade of Cured Product: Dental Composite Resin

A cover glass was placed on a glass slide, and, with a stainless-steelmold (Ø=10 mm, thickness=1 mm) set on the cover glass, the dentalcomposite material obtained in each Example and Comparative Example wasfilled into the mold until there was a slight overflow. With anothercover glass and an overlying glass slide placed on the compositematerial, a downward force was applied to push out the excess compositematerial from the mold. The composite material was then cured byapplying light for 10 seconds, using a dental visible-lightphotoirradiator (PenCure 2000, manufactured by J. Morita Corp.). Aftercuring, the cover glasses, glass slides, and mold were removed to obtaina cured product specimen.

The shade of the cured product was evaluated with a spectrophotometer(SE 6000, manufactured by Nippon Denshoku Industries Co., Ltd.).Specifically, the cured product was measured for lightness (L*/w) andchromaticities (a*/w and b*/w), which represent a lightness index L* andchromaticities a* and b*, respectively, in the L*a*b* color system ofJIS Z 8781-4:2013 in a measurement of chromaticity against a standardwhite plate placed behind the specimen. The cured product was alsomeasured for lightness (L*/b), which represents a lightness index L* inthe L*a*b* color system in a measurement of chromaticity against astandard black plate placed behind the same specimen. The difference ΔL*of L*/w and L*/b was calculated as an index of transparency (N=1).

Shade of Cured Product: Dental Mill Blank

A plate-shaped specimen (measuring 10 mm×10 mm×1.2 mm) was prepared froma cured product of the dental curable composition produced in eachExample and Comparative Example, using a diamond cutter. A flat surfaceof the specimen was ground in succession with abrasive papers #1500,#2000, and #3000, in this order, under dry conditions, until thespecimen had an adjusted thickness of 1.0 mm. The shade of the specimenwas then measured with a spectrophotometer (SE 6000, manufactured byNippon Denshoku Industries Co., Ltd.), in the same manner as in themeasurement of the dental composite resin (N=1).

In view of aesthetics, the preferred value of L*/w for the dentalcomposite resin and the dental mill blank is 80 or more, more preferably82 or more, even more preferably 85 or more, particularly preferably 87or more. L*/w may be as high as 98. The value of a*/w indicates theintensity of red color, with lower a*/w values indicating strongershades of green, and higher a*/w values indicating stronger shades ofred. In view of aesthetics, the preferred value of a*/w is higher than−10, more preferably −9 or greater, even more preferably −8 or greater.The value of a*/w is preferably 8 or less, more preferably 7 or less,even more preferably 5 or less. The value of b*/w indicates theintensity of yellow color, with lower b*/w values indicating strongershades of blue, and higher b*/w values indicating stronger shades ofyellow. In view of aesthetics, the preferred value of b*/w is 0 orgreater, more preferably 2 or greater, even more preferably 5 orgreater. The value of b*/w is preferably 30 or less, more preferably 25or less, even more preferably 20 or less. Higher values of ΔL* meanshigher transparencies. In view of aesthetics, the preferred value of ΔL*is 15 or greater, more preferably 20 or greater, even more preferably 25or greater. ΔL* may be as high as 50.

Discoloration Resistance of Cured Product

From each dental composite resin and dental mill blank, three specimenswere prepared using the same method used in the shade evaluation ofcured products, and L*/w, a*/w, and b*/w were measured in the samemanner to determine initial lightness and initial chromaticities. As atest of durability, one of the specimens was stored in water at 37° C.for 30 days, and another specimen was stored at 60° C. for 30 days underdry conditions. The remaining one specimen was exposed to xenon light inwater at 150,000 lx illuminance for 24 hours, using an acceleratedweathering tester (SOLARBOX 1500e, manufactured by CO.FO.ME.GRA). Aftertesting, each specimen was measured for L*/w, a*/w, and b*/w, and thedifferences ΔL*, Δa*, and Δb* from the initial lightness and initialchromaticities were determined. From the calculated values, a colordifference ΔE*={(ΔL*)²+(Δa*)²+(Δb*)²}^(1/2) was determined as an indexof discoloration resistance after durability test. Lower values of ΔE*mean that the discoloration resistance is higher. The preferred value ofΔE* is 7 or less, more preferably 6 or less, even more preferably 5 orless. The results of the measurements are presented in Table 1, with“Cured product after 30 days at 37° C., wet” indicating the results forspecimens stored in water at 37° C. for 30 days, and “Cured productafter 30 days at 60° C., dry” indicating the results for specimensstored at 60° C. for 30 days under dry conditions. The heading “Aftersun test” indicates the results for specimens exposed to xenon light inwater for 24 hours. The initial lightness and initial chromaticities arewith reference to specimens stored in water at 37° C. for 30 days,specimens stored at 60° C. for 30 days under dry conditions, andspecimens exposed to xenon light, before storage under these respectiveconditions.

Fluorescence of Cured Product

From each dental composite resin and dental mill blank, a single plateof specimen was prepared using the same method used in the shadeevaluation of cured products. Separately, an extracted human tooth wasground to prepare a 1 mm-thick human tooth specimen. The cured productspecimen and the human tooth specimen were observed under the light of ablacklight (FL20S BLB, manufactured by Toshiba Lighting and TechnologyCorporation), and the fluorescence intensities of these specimens werevisually compared. The specimens were scored according to the followingcriteria.

2: The fluorescence intensity of cured product specimen is comparable tothat of human tooth specimen.

1: The fluorescence intensity of cured product specimen is inferior tothat of human tooth specimen.

0: Fluorescence is not observable in cured product specimen.

The cured product specimen was also tested by being exposed to xenonlight for 24 hours using the same method used for the evaluation ofdiscoloration resistance. The cured product specimen was then evaluatedby scoring the fluorescence in the same fashion. The preferredfluorescence score is 2. The results are presented in Table 1, with“Initial” indicating the measurement results for specimens before24-hour exposure to xenon light, and “After sun test” indicating themeasurement results after 24-hour exposure to xenon light.

Ease of Polishing of Cured Product

For dental composite resins, the dental curable composition obtained ineach Example and Comparative Example was filled into apolytetrafluoroethylene mold (inner diameter 10 mm×thickness 2.0 mm).After applying light for 10 seconds with a dental visible-lightphotoirradiator (PenCure 2000, manufactured by J. Morita Corp.), thecured product was taken out of the mold as a specimen. For dental millblanks, a plate-shaped specimen (10 mm×10 mm×2.0 mm) was cut out using adiamond cutter. A flat surface of each specimen was ground with #600abrasive paper under dry conditions. After grinding, the surface waspolished wet with a silicone point, brown (M2 HP, manufactured by ShofuInc.) at a rotational speed of about 5,000 rpm for 10 seconds, and thenwith a silicone point, blue (M3 HP, manufactured by Shofu Inc.) at arotational speed of about 5,000 rpm for 10 seconds, using a laboratorymicromotor Volvere RX (manufactured by NSK). The glossiness of thepolished surface was then measured with a gloss meter (VG-2000,manufactured by Nippon Denshoku Industries Co., Ltd.; a measurementangle of 60 degrees), and a percentage of glossiness relative to theglossiness of a mirror was determined as an index of ease of polishingof the cured product (N=3). The preferred glossiness is 30% or greater,more preferably 35% or greater, even more preferably 40% or greater,particularly preferably 50% or greater.

Method of Measurement of Radiopacity of Cured Product

For dental composite resins, the dental curable composition was curedwith a dental visible-light photoirradiator (PenCure 2000, manufacturedby J. Morita Corp.) to prepare a cured product specimen (1.5 mm indiameter×1.0 mm). For dental mill blanks, a plate-shaped specimen (10mm×10 mm×1.0 mm) was cut out using a diamond cutter. The specimen waspositioned at the center of an X-ray film (occlusal Ultra-speed DF-50,manufactured by Carestream Health) alongside an aluminum step wedge, andwas irradiated with X-rays using a digital X-ray imager (Max DC70,manufactured by MORITA MFG. CORP.), with the target-film distance set at400 mm and the tube voltage set to 70 kV. After developing, fixing, anddrying the exposed film, the image density of the specimen was measuredat 20 points with an optical densitometer (DENSITOMETER PDA-85,manufactured by Kodak; measurement area=3 mm in diameter). The imagedensity of the specimen was then compared with the image density at eachthickness of the aluminum step wedge to determine the radiopacitycorresponding to the thickness of the aluminum plate (N=1). Thepreferred radiopacity is 1.0 mm or greater, more preferably 1.3 mm orgreater, even more preferably 1.5 mm or greater. The radiopacity may be2.0 mm or greater, or 3.0 mm or greater.

Materials

Polymerizable Monomer (A)

D2.6E: 2,2-Bis(4-methacryloyloxypolyethoxyphenyl)propane (average numberof moles of ethyleneoxy group added: 2.6)

Bis-GMA: 2,2-Bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane

UDMA: 2,2,4-Trimethylhexamethylenebis(2-carbamoyloxyethyl)dimethacrylate

3G: Triethylene glycol dimethacrylate

TCDDMA: Tricyclodecane dimethanol dimethacrylate

Inorganic Filler (B)

The fillers obtained in the Production Examples below were used.Commercially available fillers were also used, without anypre-conditioning.

Production Example 1 Production of B-1 (Silica-Zirconia)

Zirconium oxynitrate (32.5 g) was dissolved in 325 g of distilled water.While stirring the solution, 425 g of a commercially available silicasol (SNOWTEX OL, manufactured by Nissan Chemical Corporation) wasgradually added to obtain a mixture. A mixture powder obtained by freezedrying the mixture was then charged into an alumina crucible. Afterheating the crucible in an electric furnace at a rate of temperatureincrease of 2° C./min, the powder was fired at 600° C. for 1 hour, andpulverized for 240 minutes with a planetary ball mill (Classic Line P-6,manufactured by Fritsch; zirconia ball). After pulverization, the powderwas hydrophobized in a surface treatment using 10 parts by mass of3-methacryloyloxypropyltrimethoxysilane (KBM-503, manufactured byShin-Etsu Chemical Co., Ltd.) for 100 parts by mass of the powder. Thisproduced an inorganic filler (B-1). The inorganic filler (B-1) had anaverage particle diameter of 3.0 μm, and a specific surface area of 146m²/g.

Production Example 2 Production of B-2 (Alumina)

An inorganic filler (B-2) was produced by a surface treatment of 100parts by mass of an alumina fine powder (AEROXIDE Alu C, manufactured byNippon Aerosil Co., Ltd.) with 20 parts by mass ofγ-methacryloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-EtsuChemical Co., Ltd.). The inorganic filler (B-2) had an average particlediameter of 0.02 μm, and a specific surface area of 100 m²/g.

Production Example 3 Production of B-3 (Barium Glass)

A three-neck flask was charged with 100 parts by mass of a commerciallyavailable barium glass (GM27884 NanoFine 180, manufactured by Schott), 7parts by mass of 3-methacryloyloxypropyltrimethoxysilane (KBM-503,manufactured by Shin-Etsu Chemical Co., Ltd.), and 173 parts by mass oftoluene, and the mixture was stirred at room temperature for 2 hours.After removing toluene by distillation under reduced pressure, thecontents were vacuum dried at 40° C. for 16 hours, and heated at 90° C.for 3 hours to obtain an inorganic filler (B-3) having a surface-treatedlayer. The inorganic filler (B-3) had an average particle diameter of0.2 μm, and a specific surface area of 35 m²/g.

Production Example 4 Production of B-4 (Organic-Inorganic CompositeFiller)

For production of B-4, 100 parts by mass of the inorganic filler (B-3)was added and mixed into 100 parts by mass of a polymerizable monomermixture of Bis-GMA and 3G (mass ratio 1:1) containing 1 mass % ofazobisisobutyronitrile (AIBN) dissolved in advance as a polymerizationinitiator. After preparing the mixture into a paste form, the paste wassubjected to 5 hours of thermal polymerization at 100° C. in a reducedpressure atmosphere. The resulting product of polymerization and curewas pulverized with a vibration ball mill until the powder had anaverage particle diameter of about 5 μm. For surface treatment, 100parts by mass of the powder was refluxed at 90° C. for 5 hours in a 2mass % ethanol solution of γ-methacryloyloxypropyltrimethoxysilane(KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.). This producedan organic-inorganic composite filler as inorganic filler (B-4). Theinorganic filler (B-4) had an average particle diameter of 5.2 μm, and aspecific surface area of 35 m²/g.

Production Example 5 Production of B-5 (Silica-Ytterbia)

The water in a commercially available silica-ytterbium oxide aqueousdispersion (SG-YBSO30SW, manufactured by Sukgyung AT) was removed bydistillation using an evaporator, and the resulting solid component waspulverized for 180 minutes with a planetary ball mill (Classic Line P-6,manufactured by Fritsch; zirconia ball). The powder was then fired for 1hour in an electric furnace set at 800° C., and pulverized for 180minutes using the same planetary ball mill. The powder was hydrophobizedin a surface treatment using 10 parts by mass of3-methacryloyloxypropyltrimethoxysilane (KBM-503, manufactured byShin-Etsu Chemical Co., Ltd.) for 100 parts by mass of the powder. Thisproduced an inorganic filler (B-5). The inorganic filler (B-5) had anaverage particle diameter of 5.7 μm, and a specific surface area of 95.8m²/g.

B-6 (Ytterbium Fluoride)

A silica-coated ytterbium fluoride (SG-YBF100WSCMP10, manufactured bySukgyung AT) was used without any pre-conditioning. The silica-coatedytterbium fluoride had an average particle diameter of 100 nm, and aspecific surface area of 14.2 m²/g.

Polymerization Initiator (C)

CQ: Camphorquinone

TPO: 2,4,6-Trimethylbenzoyldiphenylphosphine oxide

THP: 1,1,3,3-Tetramethylbutyl hydroperoxide

Fluorescent Agent (D-1)

D-1-1: 2-(2-Hydroxyphenyl)-4(1H)-quinazolinone (formula (9))

D-1-2: N-[2-(4-Oxo-1,3-benzoxazin-2-yl)phenyl]benzenesulfoneamide(formula (10))

D-1-3:7-Dimethylamino-3-[2-[4-(trifluoromethyl)phenyl]ethenyl]-2H-1,4-benzoxazin-2-one(formula (11))

Fluorescent Agent (D-2)

D-2-1: 1,4-Bis(2-benzoxazolyl)naphthalene (formula (12))

Fluorescent Agent (D-3)

D-3-1: Diethyl 2,5-dihydroxyterephthalate

Polymerization Accelerator (E)

PDE: Ethyl 4-(N,N-dimethylamino)benzoate

Additive (F)

BHT 3,5-Di-t-butyl-4-hydroxytoluene (polymerization inhibitor)

TIN: Tinuvin 326 (manufactured by BASF Japan; ultraviolet absorber)

Examples 1 to 6 and Comparative Examples 1 to 6 (Dental Composite Resin)

The materials shown in Table 1 were mixed and kneaded in the dark atordinary temperature (23° C.) in the proportions shown in the table.After homogenization, the product was degassed in vacuum to preparedental curable compositions. The dental curable compositions were thentested using the methods described above. The results are presented inTable 1.

Example 7 and Comparative Examples 7 and 8 (Dental Mill Blank)

The materials shown in Table 1 were mixed and kneaded in the dark atordinary temperature (23° C.) in the proportions shown in the table.After homogenization, the product was degassed in vacuum to preparedental curable compositions. The dental curable composition was chargedinto a rectangular mold measuring 20 mm×30 mm×60 mm, and was heated at50° C. for 1 hour. This was followed by a heat treatment performed at150° C. for 1 hour under an applied pressure of 5 MPa. The resultingcured product was obtained as a dental mill blank. The cured product ofthe dental curable composition was tested using the methods describedabove. The results are presented in Table 1.

TABLE 1 Example 1 2 3 4 5 Polymerizable monomer (A) D2.6E Based on 80 8080 80 60 Bis-GMA total mass of 20 UDMA polymerizable 3G monomer (A) 2020 20 20 20 TCDDMA at 100 parts by mass [parts by mass] Parts by massbased on 100 parts by mass of (A) + (B) 25 25 25 25 9 Inorganic filler(B) B-1 (Silica-zirconia) [parts by 64 64 64 64 B-2 (Alumina) mass] 18B-3 (Barium glass) 18 B-4 (Organic-inorganic composite filler) 55 B-5(Silica-ytterbia) B-6 (Ytterbium fluoride) 11 11 11 11 Polymerizationinitiator (C) CQ Relative to 0.3 0.3 0.3 0.3 0.5 TPO total 100 0.2 0.20.2 0.2 0.5 THP parts by Fluorescent agent (D-1) D-1-1 mass of 0.05 0.050.05 D-1-2 polymerizable 0.04 D-1-3 monomer (A) 0.05 Fluorescent agent(D-2) D-2-1 [parts by 0.02 Fluorescent agent (D-3) D-3-1 mass]Polymerization accelerator (E) PDE 0.3 0.3 0.3 0.3 1.0 Additive (F) BHT0.05 0.05 0.05 0.05 0.05 TIN 0.5 0.5 0.5 0.5 0.5 Shade L*/w 89.5 89.789.1 89.0 87.1 a*/w −6.3 −3.6 −6.3 −7.1 −7.9 b*/w 12.5 9.7 13.5 14.719.4 ΔL* 28.6 28.5 29.1 28.4 24.1 Discoloration resistance Cured productafter 30 days at 37° C., wet ΔE* 2.3 1.4 3.3 1.7 2.5 Cured product after30 days at 60° C., dry 3.7 2.4 4.1 2.9 3.1 After sun test 1.8 1.6 2.42.0 2.8 Fluorescence Initial (Score) 2 2 2 2 2 After sun test 2 2 2 2 2Flexural strength [MPa] 149 152 158 152 128 Ease of polishing [%] 59 6365 58 82 Radiopacity [%] 2.0 2.0 2.0 2.0 1.3 Example Comparative Example6 7 1 2 3 Polymerizable monomer (A) D2.6E Based on 45 80 80 60 Bis-GMAtotal mass of 20 UDMA polymerizable 70 3G monomer (A) 30 20 20 20 TCDDMAat 100 parts 55 by mass [parts by mass] Parts by mass based on 100 partsby mass of (A) + (B) 25 33 25 25 9 Inorganic filler (B) B-1(Silica-zirconia) [parts by 67 64 64 B-2 (Alumina) mass] 18 B-3 (Bariumglass) 18 B-4 (Organic-inorganic composite filler) 55 B-5(Silica-ytterbia) 75 B-6 (Ytterbium fluoride) 11 11 Polymerizationinitiator (C) CQ Relative to 0.4 0.3 0.3 0.5 TPO total 100 0.4 0.2 0.20.5 THP parts by 1.0 Fluorescent agent (D-1) D-1-1 mass of 0.05 D-1-2polymerizable 0.04 D-1-3 monomer (A) Fluorescent agent (D-2) D-2-1[parts by Fluorescent agent (D-3) D-3-1 mass] 0.05 Polymerizationaccelerator (E) PDE 0.4 0.3 0.3 1.0 Additive (F) BHT 0.05 0.05 0.05 0.05TIN 0.5 0.5 0.5 0.5 0.5 Shade L*/w 89.9 96.7 90.0 89.2 87.3 a*/w −4.7−3.8 −1.5 −10.0 −5.8 b*/w 19.0 14.8 8.0 20.8 16.0 ΔL* 32.1 33.1 28.129.1 24.3 Discoloration resistance Cured product after 30 days at 37°C., wet ΔE* 2.1 1.1 0.5 5.4 1.1 Cured product after 30 days at 60° C.,dry 3.2 2.5 2.7 6.9 0.9 After sun test 3.8 0.2 1.8 6.4 3.0 FluorescenceInitial (Score) 2 2 0 2 0 After sun test 2 2 2 Flexural strength [MPa]143 187 153 157 125 Ease of polishing [%] 76 67 56 57 79 Radiopacity [%]3.4 1.4 2.0 2.0 1.3 Comparative Example 4 5 6 7 8 Polymerizable monomer(A) D2.6E Based on 60 45 45 Bis-GMA total mass of 20 UDMA polymerizable70 70 3G monomer (A) 20 30 30 TCDDMA at 100 parts 55 55 by mass [partsby mass] Parts by mass based on 100 parts by mass of (A) + (B) 9 25 2533 33 Inorganic filler (B) B-1 (Silica-zirconia) [parts by 67 67 B-2(Alumina) mass] 18 B-3 (Barium glass) 18 B-4 (Organic-inorganiccomposite filler) 55 B-5 (Silica-ytterbia) 75 75 B-6 (Ytterbiumfluoride) Polymerization initiator (C) CQ Relative to 0.5 0.4 0.4 TPOtotal 100 0.5 0.4 0.4 THP parts by 1.0 1.0 Fluorescent agent (D-1) D-1-1mass of D-1-2 polymerizable D-1-3 monomer (A) Fluorescent agent (D-2)D-2-1 [parts by Fluorescent agent (D-3) D-3-1 mass] 0.05 0.05 0.05Polymerization accelerator (E) PDE 1.0 0.4 0.4 Additive (F) BHT 0.050.05 0.05 TIN 0.5 0.5 0.5 0.5 0.5 Shade L*/w 87.2 90.5 90.2 96.3 96.2a*/w −9.9 −3.8 −8.4 −2.3 −6.2 b*/w 23.0 15.2 26.5 8.4 21.9 ΔL* 24.1 30.831.2 34.3 35.8 Discoloration resistance Cured product after 30 days at37° C., wet ΔE* 14.8 0.5 9.0 0.4 3.2 Cured product after 30 days at 60°C., dry 16.6 1.8 12.4 2.1 5.5 After sun test 9.6 1.5 10.3 1.4 4.8Fluorescence Initial (Score) 2 0 2 0 2 After sun test 2 2 2 Flexuralstrength [MPa] 123 146 140 190 186 Ease of polishing [%] 84 71 70 65 68Radiopacity [%] 1.3 3.4 3.4 1.4 1.4

As shown in Table 1, the dental curable compositions of the presentinvention showed desirable shades in the cured products, and haddesirable discoloration resistance, without losing fluorescence evenafter the light resistance test. Particularly, in Example 5, the curedproduct had reduced discoloration (yellowing), despite containingalumina as inorganic filler. As can be seen from these results, thecured products of the dental curable compositions of the presentinvention have a high flexural strength, and are easily polishable toproduce sufficient glossiness by simple polishing.

INDUSTRIAL APPLICABILITY

A dental curable composition of the present invention can produce acured product that shows sufficient fluorescence, and that excels inaesthetics and durability while having sufficient mechanical strengthand retaining ease of polishing. This makes a dental curable compositionof the present invention suitable for use in applications such as dentalcomposite resins and dental mill blanks.

1: A dental curable composition comprising a polymerizable monomer (A),an inorganic filler (B), a polymerization initiator (C), and afluorescent agent (D), wherein the fluorescent agent (D) comprises a 9-to 11-membered benzo-fused heterocyclic compound containing two or moreheteroatoms excluding benzoimidazole compounds. 2: The dental curablecomposition according to claim 1, wherein the 9- to 11-memberedbenzo-fused heterocyclic compound containing two or more heteroatomscomprises a fluorescent agent (D-1) representing a benzo-fused6-membered heterocyclic compound having two heteroatoms. 3: The dentalcurable composition according to claim 2, wherein the fluorescent agent(D-1) comprises a compound having a benzodiazinone skeleton, and/or acompound having a benzoxazinone skeleton. 4: The dental curablecomposition according to claim 3, wherein the compound having abenzodiazinone skeleton is a compound having a skeleton represented bythe following general formula (5),

wherein X represents a 6-membered heterocyclic ring having two nitrogenatoms, and the 6-membered heterocyclic ring has at least one oxo group,and may be optionally substituted. 5: The dental curable compositionaccording to claim 3, wherein the compound having a benzodiazinoneskeleton is a compound (D-1a) having a quinazolinone skeleton. 6: Thedental curable composition according to claim 3, wherein the fluorescentagent (D-1) comprises a compound having a benzoxazinone skeleton. 7: Thedental curable composition according to claim 6, wherein the compoundhaving a benzoxazinone skeleton is a compound having a skeletonrepresented by the following general formula (6),

wherein Y represents a 6-membered heterocyclic ring having one nitrogenatom and one oxygen atom, and the 6-membered heterocyclic ring has atleast one oxo group, and may be optionally substituted. 8: The dentalcurable composition according to claim 2, wherein the fluorescent agent(D-1) is a compound having a moiety represented by the following generalformula (1) or (2),

wherein R¹ in general formulae (1) and (2) is an oxygen atom or —NH—,and R² in general formulae (1) and (2) represents an optionallysubstituted aromatic group. 9: The dental curable composition accordingto claim 2, wherein the fluorescent agent (D-1) comprises at least onecompound selected from the group consisting of2-(2-hydroxyphenyl)-4(1H)-quinazolinone,2-(2-hydroxyphenyl)-4H-3,1-benzoxazin-4-one,N-[2-(4(1H)-quinazolinon-2-yl)phenyl]benzenesulfoneamide,N-[2-(4-oxo-1,3-benzoxazin-2-yl)phenyl]benzenesulfoneamide,7-dimethylamino-3-[2-[4-(trifluoromethyl)phenyl]ethenyl]-2H-1,4-benzoxazin-2-one,7-dimethylamino-3-[2-[2,3,4,5,6-pentafluorophenyl]ethenyl]-2H-1,4-benzoxazin-2-one,and7-dimethylamino-3-[2-[2,4-bis(trifluoromethyl)phenyl]ethenyl]-2H-1,4-benzoxazin-2-one.10: The dental curable composition according to claim 2, wherein thefluorescent agent (D) further comprises a fluorescent agent (D-2)representing a benzo-fused 5-membered heterocyclic compound having onenitrogen atom and one oxygen atom. 11: The dental curable compositionaccording to claim 10, wherein the fluorescent agent (D-2) is afluorescent agent (D-2a) representing a compound having a benzoxazoleskeleton. 12: The dental curable composition according to claim 11,wherein the fluorescent agent (D-2a) is a compound having a moietyrepresented by the following general formula (3),

wherein R³ represents an optionally substituted aromatic group, or anoptionally substituted vinylene group. 13: The dental curablecomposition according to claim 11, wherein the fluorescent agent (D-2a)is a compound represented by the following formula (12)

14: The dental curable composition according to claim 1, wherein theinorganic filler (B) is an inorganic filler containing at least onemetal compound selected from the group consisting of zirconium oxide,aluminum oxide, ytterbium oxide, and ytterbium fluoride. 15: The dentalcurable composition according to claim 1, wherein the inorganic filler(B) has a specific surface area of 10 to 300 m²/g. 16: A dentalcomposite resin comprising a dental curable composition of claim
 1. 17:A dental mill blank comprising a cured product of a dental curablecomposition of claim 1.